| Description | Comprising certificates issued by the Ministry of Housing and Local Government for the collieries of Avenue Carbonization Plant, 1955-1957, Blackwell Coke Ovens, 1950-1955, Grassmoor Coke Ovens, 1950-1957, Harworth Coke Ovens, 1950-1957, Clay Cross Coking Plant, 1950-1952, and Hardwick Coal Ovens and Cokiing PLant, 1950-1957 |