Few more thoughts on checks. eBay chaps first attempts were a plain brass blank with copper numbers soldered to them. Very catchy looking but complete figments, problem being this is maybe 15 plus years ago, they're still out there and people will be looking to unload.
Re-strikes, about 30 plus years ago, a collector got hold of some original dies and commissioned a company to produce a fair number of checks.
Pits include Pope & Pearsons West Riding Coll (Yorkshire diamond) Hemsworth Coll (round) + one other that I've forgotten. He also had the company make a completely fictitious check Churwell Coll Leeds.
The way to detect the Hemsworth is that the numbering on originals is nicely machine engraved, the re-strikes are punched.
"Pairs " of checks (yeah, right) one is original, the other is blank unissued that the seller has stamped to match.
Lastly "named" checks. Checks occasionally did carry a name but of the several currently on eBay, all are done with the same set of letter punches, so someone has some genuine blanks and a "Guide to the Coalfields ".
That's all I can think of that might be of use...
Regards, John...
Huddersfield, best value for money in the country, spend a day there & it'll feel like a week........