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Amgueddfa Cymru – Museum Wales
Printed in black ink with handwritten details. Sixteen circular graphs - 'Simmance's Deadbeat Recorder'. Dates given on the graphs are for January 1935. Loose within a green card file with all other documents with accession number 83.184I/67. The file is labelled 'Colliery Boiler Plant B31', 'Cefn Coed Data' and 'Colliery Engineering'.
