Dated N.C.B. mining checks or Fobs

Can any one throw any light on the following dated N.C.B. checks? All are brass embossed, 32 mm in diameter and have no stamped identification numbers on them.

I am note sure why they were made and what purposed they served. It is possible that they were some sort of commemorative or promotional fobs issued by the Board to various of its employees. I also think there is a good chance that they originated from the Doncaster area as I have seen similar mystery commemorative checks/fobs, some with dates, which obviously originated from the South Yorkshire area at about the same time (i.e. early 1980s). A few of these are shown below.

I'm fairly sure the Grimethorpe check was issued as a commemorative key fob which was given to men who worked at that particular pit in celebration of the occasion of the colliery producing its first million tonnes of ROM coal in 1980. As for the other examples shown above I'm note sure. They are obviously from the South Yorkshire or Doncaster area but what were they used or issued for? Can anyone tell me? Maybe someone could identify or link the telephone number (?) embossed on one of these checks/fobs with a particular colliery or area administration office? Has anyone got access to a "Guide To The Coalfields" for the early 1980s where such telephone numbers are listed by N.C.B. Areas - if so could you please try and look up this number for me.