Correspondence of the Butterley Company on the valuation of collieries and equipment for rating and income tax purposes Including copy valuations of coal mines undder the Rating and Valuation Act 1925, Jan 1939, loose detailed estimated valuation of recoverable plant at the Butterley Company's pits as of 31 March 1931, and loose plan of Ollerton Colliery showing positions of all buildings (numbered but not identified), 1930s May 1931-Jun 1946