Dr. B.P. Saraf, J.:- The sole paint for consideration in this case is whether the impugned orders of assessment are barred by Limitation laid down in Rule 10 of the Central Excise Rules, 1944. 2. The petitioner Company herein-after the ''assessee" carried on business, inter alia, of manufacture and sale of petroleum products including Bitumen. On 2. 2. 67 a dispute arose in regard to the classification of certain variety of Bitumen manufactured by the petitioner. The said item was earlier assessed as "Bitumen Straight Grade" at a specific rate of Duty. A sample was taken of the particular variety of Bitumen on 2. 2. 67. It was tested by the Chief Chemist of Central Excise who reported and opined that it was not "Bitumen Straight Grade but Bitumen blown Grade and therefore, assessable at higher rate of duty. On receiving the aforesaid report, the con­cerned Superintendent of Central Excise wrote to the assessee informing the contents of the chemical analysis report as also the inte­ntion of the Department to reassess the goods at the a devalue rate on the basis of the new classification. The assessee objected to the classification made by the Department and preferred an appeal against the decision. The Superintendent of Central Excise in view of the controversy in regard to the classification of the excisable goods, by letter dated 20. 9. 67 addressed to the assessee, directed that the assessments made in respect of Bitumen other than Cutback and Earth Oil since 2. 2. 67 shall be treated as provisional and that the cases would be finalized after final decision over the product. In the mean time, Self Removable Procedure hereinafter 'SRP' was int­roduced with effect from 1. 8. 69 in respect of mineral Oil. Under the said procedure the manufacturer was required to submit classi­fication list in respect of each product as per the provisions of the Rules. The assessee submitted classification lists which were accepted "provisionally" and it was ordered that the assessments of the goods were to be made provisionally under Rule 9 (B) of the Central Excise Rules, 1944, hereinafter the 'Rules'. In the classification lilts subm­itted by it from time to time, the assessee also recorded against Blown Grade Bitumen 'classification is disputed'. This system Cont­inued till the impugned action was taken for finalizing the assess­ments. In the classification lilts subm­itted by it from time to time, the assessee also recorded against Blown Grade Bitumen 'classification is disputed'. This system Cont­inued till the impugned action was taken for finalizing the assess­ments. In the meantime, the Revision Petition filed by the assessee was decided by the Government of India by order dated 24.11.72. It was held that the term Bitumen Straight Grade covers Blown Bitumen. However, despite the aforesaid decision the assessee cont­inued to submit the classification list as in the past. No revised classification lists in terms of the aforesaid order passed on revision were submitted. The assessment also continued to be made as before. 3. On 7.10.78, the assessee submitted revised classification lists based on the revisional order passed by the Government of India. The said revised classification lists were approved by the Department on 4.1.79. Thereafter a show cause notice dated 22.1.79 was issued whe­reby the assessee was informed that it was proposed to finalize the provisional assessments of Bitumen (other then Cutback and Earth Oil) for the period from 2.2.67 to 28.2.78 by recalculation of the duty ele­ments of the products prescribed for Straight Grade. The additional Duty payable on finalization of the provisional assessments was calculated' at Rs. 1,12,00,105.99. In the sail notice the entire background and history of the case was stated. It was categorically stated in the notice that the original assessments which were provisional were sought to be finalised. However, in the beginning of the said notice, a reference was made to Rule 10 (i) of the Rules and it was stated that the dues mentioned in the notice were recoverable from the peti­tioner under the said Rule. The assessee objected to the recalcula­tion of duty on the ground, inter-alia, that the impugned notice was barred by limitation as according to it, the original assessme­nts were not provisional but final. It was contended that no amount was payable as stated in the said notice. The Assistant Collector of Customs, Central Excise, Dibrugarh on consideration of the objections raised by the petitioner held" that the assessments were provisional ass­essments and, as such, the same could be finalised without resort of Rule 10 of the Rules. He therefore, confirmed the demand for realisation of the additional duty amounting to Rs. 1,12,00,105.99. The assessee filed appeal against the said order to the appellate Collector, Central Excise, Calcutta which was also rejected. He therefore, confirmed the demand for realisation of the additional duty amounting to Rs. 1,12,00,105.99. The assessee filed appeal against the said order to the appellate Collector, Central Excise, Calcutta which was also rejected. There­after a revision petition was filed against the said order before the Government of India. The Revisional Authority considered the objec­tion' of the petitioner relating to the quantum of the demand and allowed relief on that score. The demand was reduced from Rs. 1,12,00,105.99 to Rs. 40,29,655.54. The submission of the assessee to the effect that the assessments were barred by limitation was, however rejected on the ground, inter-alia, that the assessments for the rele­vant periods were provisional and, as such, the same were rightly finalised by the authority. The period of limitation prescribed under Rule 10 did not apply in such a case. The assessee thereafter cha­llenged the aforesaid order before this court by filing the present writ petition. 4. The sale contention of the petitioner is that the levy is ba­rred by limitation under Rule 10 and that the original assessments could not be termed as ''provisional assessments" as the conditions laid down under Rule 9 B were not satisfied. 5. We have heard Mr. J. P. Bhattacharjee, learned counsel for the petitioner. Also heard Mr. S.k. Chandmahammad, Sr. Central Government Standing Counsel. The learned counsel for the petitioner contended that the assessments for the periods from 2.2.67 to 15.12.77 were not provisional as the conditions laid down in Rule 9B which provides for such assessments were not fulfilled. They were final. As such, if it found that there is any short levy, action could be tak­en only under Rule 10 of the Rules which provides a period of limitation of three months from the date of payment of Excise Duty. It was, therefore, submitted that the impugned notice dated 22.1.79 informing the petitioner about the proposed recalculation of dues itself was barred by limitation and, as such, all subsequent orders recalculating the demand, on the basis thereof the appellate and revisional orders confirming the aforesaid action are illegal and witho­ut jurisdiction. In support of the aforesaid submissions, Mr. Bhattacharjee placed reliance the impugned notice dated 22.1.79 wherein the authority itself had referred to Rule 10 of the Rules. In support of the aforesaid submissions, Mr. Bhattacharjee placed reliance the impugned notice dated 22.1.79 wherein the authority itself had referred to Rule 10 of the Rules. It was submitted that the said notice itself clearly goes to show that the action under challenge was taken under Rule 10 and it was not open to the authorities to contend that it was not a case of assessment of short levy etc. as contemplated by Rule 10 of the Rules but sim­ple case of finalization of provisional assessment for which no peri­od of limitation was prescribed. 6. We have carefully considered the submissions of the learned counsel for the petitioner. We have perused the provisions of Rule 9B and 10 of the Rules. Rule 10 lays down the procedure for rec­overy of dues not levied or paid or short levied or not paid in full or erroneously refunded. The said Rule was substituted with effect from 7.8.77 and substituted rule remained in force till 16. 11. 80 on and from 17.11.80 the provision contained in Rule 10 were incorpo­rated in the Act itself by insertion of new Sections namely 11 (A) and H(B). It is not necessary to discuss the provisions of these sections as the same are not relevant for the present case. Rule 10 as substituted with effect from 7.8.77, is relevant for our present purpose. It is not necessary to discuss the provisions of these sections as the same are not relevant for the present case. Rule 10 as substituted with effect from 7.8.77, is relevant for our present purpose. The same is reproduced below :- ''Rule-10.Recovery of duties not levied or not paid, or short levied or not paid in full or erroneously refunded: (i) Where any duty has not been levied or paid or has been short levied or erroneously refunded or any duty assessed has not been paid in full, the proper officer may, within six months from the relevant date serve notice on the person chargeable with the duty which has not been levied or paid, or which has been short-levied, or to whom the refund has erroneously been made, or which has not been paid in full, requiring him to show cause why he should not pay the amo­unt specified in the notice provided that : (a) Where any duty has not been levied, or paid, or has been short levied or has not been paid in full, by reason of fraud, collusion or any willful misstatement or suppression of facts by such person or his agent, or (b) Where any person or his agent, contravenes any of the provisions of those rules with intent to evade payment of duty and has not paid the duty in full or ; (c) Where any duty has been erroneously refunded by reason of collusion or any willful misstatement or suppression of facts by such person or his agent, the provisions of this sub--section, shall in any of the cases referred to above, have-effect as if for the words 'six months' the words 'five years' were substituted ". Rule 10 thus specified a period of limitation for taking action there under and that period is six months from the relevant date. ''Relevant date" has been defined in explanation (2)(ii). Clause (b) of the note thereof provides that relevant dates means-''in the case of excisable goods on which the value of or the rate of duty has been provisionally Determined under these rules the date on which the duty is adjusted after final determination of the value of the rate of the duty, as the case may be''. Clause (b) of the note thereof provides that relevant dates means-''in the case of excisable goods on which the value of or the rate of duty has been provisionally Determined under these rules the date on which the duty is adjusted after final determination of the value of the rate of the duty, as the case may be''. Rule 10 makes it clear that in a case where the value or the duty in respect of any exposable goods has been determined provisionally limitation will apply only from the date on which the duty is adjusted after final determination of the value or the rate of duty. No. period of limitation has been laid down for finalization of provisional assessment. The provision relating to finalization of provisional assessment are contained in Rule 9B of the Rules. No. period of limitation has been laid down for finalization of provisional assessment. The provision relating to finalization of provisional assessment are contained in Rule 9B of the Rules. The said Rule being relevant for the present purpose is reproduced below;- "Rule-9B Provisional assessment to duty-(1) Notwithstanding anything containing in these rules.- (a) Where the proper officer is satisfied that an assesse is una­ble to produce any document or furnish any information necessary for the assessment of duty on any excisable goods ; or (b) Where the proper officer deems it necessary to subject the excisable woods to any chemical or any other test for the purpose of assessment of duty thereon ; or (c) Where an assessee has produced all the necessary docu­ments and furnished full information for the assessment of duty, but the proper officer deems it necessary to make further inquiry (including the enquiry to satisfy himself about the due observance of the conditions imposed in respect of the foods after their removal) for assessing the duty the proper officer may, either on a written request made by the assessee or on his own accord, direct that the duty livable on such goods shall, pending the production of such documents or furnishing of such information or completion of such test or enquiry, be asse­ssed provisionally at such rate or such value (which may not necess­arily be the rate or price declared by the assessee) as may be indicat­ed by him, if such assessee executes a bond in the proper form with such rarity or sufficient security in such amount, or under such conditions as the proper officer deems fit, binding himself for payment of the difference between the amount of duty as provisionally assessed and as finally assessed.) (2) * * * * (3) The Collector may permit the assessee to enter into a general bond in the proper form with such surety or sufficient security in such amount or under such conditions as the Collector approves for assessment of any goods provisionally from time to time. Provided that, in the event of death, insolvency or insu­fficiency of the surety or where the amount of the bond is inadequate, the Collector may in his discretion demand a fresh bond and may, if the security furnished for a bond is not adequate, demand additional security. Provided that, in the event of death, insolvency or insu­fficiency of the surety or where the amount of the bond is inadequate, the Collector may in his discretion demand a fresh bond and may, if the security furnished for a bond is not adequate, demand additional security. (4) The goods provisionally assessed under sub-rule (1) may be cleared for home consumption or exporting in the same manner as the goods which are not so assessed. (5) When the duty livable on the goods is assessed finally in accordance with the provision of those rules, the duty pro­visionally assessed shall be adjusted against the duty finally assessed and if the duty provisionally assessed falls short of, or is in excess of the duty finally assessed, the assessee, shall pay the deficiency or be entitled to a refund as the case may be." 8. Rule 9B of the Rules is a beneficial provision It empowers the authorities to direct provisional assessment of duty pending final determination of dispute where there is any dispute regarding the value of the goods or the rate of duty livable on such goods. This power has been conferred to mitigate hardship that might be caused to the assessee during the interim period. The power can be exercised suo moto or 0.1 application. While exercising this power the authority concerned may impose certain conditions in regard to furnishing security etc. to protect the interest of the revenue. Demand of security is not a condition precedent to exercise of power to order provisional assessment. It is, in fact, additional power vested in the authority which may be exercised in appropriate case to protect the interest of the revenue. An assessee, in whose favour an order for provisional assessment under Rule 9B is passed without deman­ding any security, con not, after taking benefit of the order to pay the duty at the lower rate, challenge the same when the provisio­nal assessments made in pursuance thereof are sought to be finalised. 9. In the light of the aforesaid provision contained in Rule 9B, its scheme, object and purpose, we are to consider whether the assessment made in the case of the assessee in the instant case were provisional assessments, or not. We find that all the three authori­ties examined the facts of the case at length and arrived at the conclusion that the assessments were provisional. We find that all the three authori­ties examined the facts of the case at length and arrived at the conclusion that the assessments were provisional. These were also so understood both by the Department as well as the assessee and both of them acted accordingly all through treating the same as provi­sional. The Assistant Collector of Customs and Central Excise on consideration of the facts of the case arrived' at the following con­clusion- "From all the above facts I am convinced that all assess­ments on the Bitumen other than Cutback and Earth Oil since 2.2 67 were made provisionally under Rule 9B of the Central Excise Rules 1944 and as such the party's argument that the assessments were completed and the assessments for the period is not at all correct and as such it not acceptable". 10. On appeal the appellate collector of Central Excise also-arrived at the same finding that all the assessment for the period from 2.2.67 to 15.12.77 were provisional. On Revision, the Govern­ment of India in its order dated 6th June, 1981 also recorded a categorical finding to the effect that the assessments for the releva­nt periods were provisional all throughout. In para 12 of the said order it is stated as follows :- "Meanwhile ever since the introduction of S.R.P., the peti­tioners in pursuance of the decisions of the lower authorities up to the appellate level, to treat the goods as 'blown grade bitumen' as distinguished from 'straight and cutback bitumen', filed classification lists from time to time indicating therein that the "assessment of the goods to be provisional, as the classification, of the goods was being disputed" and they also indicated therein the fact of execution of B-13 bond which is associated with provisional assessments. While approving the classification list the Assistant Collector, inter alia, made it unambiguously clear as a rule that "the tariff classification and the rate of duty leviable in respect of the goods described in is approved provisionally" and that "the assessment of the­se goods shall be made by the Central Excise Officer-in-charge provisionally under Rule 9B." 11. We have also examined the facts of the case. On perusal of the same, we find that the concurrent finding in regard to the nature of assessment arrived at by all the three authorities below is based on material and evidence on record. We have also examined the facts of the case. On perusal of the same, we find that the concurrent finding in regard to the nature of assessment arrived at by all the three authorities below is based on material and evidence on record. Besides, as observed by the authorities, the assessee itself a throughout treated the assess­ments as provisional and file the classification lists as "Provision­al". It was only on 7.10.78 that the petitioner submitted revised cla­ssification lists effective from 1.8.69 to 28.2.78 for approval which was approved by the authorities on 4.1.79. In fact, in the instant case the assessee by its own actions and conduct is estopped from raising such a contention on the ground of non-compliance of any supposed conditions laid down in Rule 9B. In view of the aforesaid factual position we do not find force in the submission of the learned counsel for the petitioner that the assessments were not provisional. 12. Before concluding, we may deal with two more submissions made by the learned counsel for the petitioner. It was contended by the learned counsel that in the impugned notice dated 22.1.79 it was stated that the amount in question was recoverable under Rule 10 (i) of the Rules which goes to show that it was a notice under the said Rule. We are not impressed by the aforesaid contention. The impugned notice is very elaborate and contains the entire background and history of the case. It is clearly stated in it that the assess­ments earlier made were provisional assessments and that it was proposed to finalise the said provisional assessments by re-calcula­ting the duty elements on the product in question. A reading of the aforesaid notice makes it abundantly clear that it was a show cause notice against proposed finalisatian of provisional assessment and not a notice under Rule 10 (1). A wrong reference to Rule 10(1) in the said notice will not to it a notice under the said rule when, in fact, it was not so and it will not invalidate the notice if it is otherwise valid. It is well settled that if the exercise of a power can be traced to a legitimate source, the fact that the same was purported to have been exercised under a different power does not vitiate the exercise of the power in question. It is well settled that if the exercise of a power can be traced to a legitimate source, the fact that the same was purported to have been exercised under a different power does not vitiate the exercise of the power in question. In the instate case, as stated earlier, the assessments in question were provisional aid the authority concerned had the power to finalise the same. The limitation prescribed in Rule 10 was not applicable to such a case. Besides the show cause notice itself was very clear and the assessee was not at all left in any doubt in regard to the nature of action contemplated by the authorities. It was stated in the notice in so many words that what was sought to be done was finalization of the provisional assessments. In view of the aforesaid fac­tual and legal position we are of the opinion that wore referen­ce of Rule 10 in the impugned notice did not in any way vitiate the proceedings in the instant case. 13. The last submission of the learned counsel was that the finding of the Revisional authority that the assessment was 'incom­petent assessment if not provisional' is not tenable in law in view of the deletion of Rule 10A of the Rules with effect from 6.8.77. We have con­sidered the submission. We find that the aforesaid observation was given by the Revisional authority while dealing with the alternative sub­mission of the revenue in regard to the source of their power to take the impugned action. As we have already approved the concurrent finding of all the three authorities below that the initial ass­essments were provisional assessments and uphold the impugned notice and orders on that ground, it is not necessary to go into the alte­rnative submissions and to decide the effect of deletion of Rule 10A of the Rules on the concept of 'incomplete assessment' as it will be purely academic. We leave it open to be decided in an appropriate case. 14. In view of the discussion made above we held that the imp­ugned orders of assessment were made in accordance with law and were not barred by limitation prescribed under Rule 10 of the Rules. 15. In the result, the writ petition is dismissed. No order as to costs.