(Split Shift Checks from South Yorkshire - Both 40 mm Diameter, Uniface, Aluminiun Embossed)
 

Does anyone know how where these type of checks used? Are there any any ex-miners out there who remember using them or anything similar?

I've only ever seen this type of check for Upton and Darfield Collieries which were both part of Area No.4 of the NCB's North Eastern Area (as defined in the 1950s/60s). Are there any more examples from other pits known?

Any information as to what this check is, what it was used for or how old it might be would be greatly appreciated.