have come into existence under section 10(1) of the Bihar Land Reforms Act and alternatively be cause by virtue of the provisions of section 30A of the 1957 Act the provisions of section 9(1) of the said Act were not applicable to or in relation to the mining leases in respect of coal granted before October 25, 1949 until the Central Government, by notification, decided otherwise; that as regards the claim in respect of the period from December 29, 1961 to December 31, 1965 'royalty at 21/2% of F.O.R. price of coal had already been paid by the respondents as per notification of the Central Government issued in exer cise of the power under section 30A of the 1957 Act and having itself invited and accepted this payment in full discharge of the respondents ' liability for royalty payable for the said period, the State was not entitled to unilater ally revoke the aforesaid discharge or satisfaction and claim further royalty at 21/2% of F.O.R. price of coal over and above what has already been paid.