I recently did a Sports Afield column on buttplates & pads and got samples of most of the available steel buttplate. (McFarland from Brownells is best.) I didn't think the Treebone all that bad, but I haven't used one either. Checkering a steel buttplate is very difficult, so much so that it is too complicated to explain the problems.
A fellow used to charge me $350, that's 15 years ago, to hand checker one. He said he did it with a chisel. I thought it extravigant, but VERY nicely done, he won't do them at any price any more. I talked with Kathy Forster about machine checkering one just last week, she said the last one she did (years ago) she wasn't at all happy with. Engraver Larry Peters sent me to Kathy when I asked him to do one.

There is Biesens' checkered steel, but the screws aren't right, need to make new screws, and the Brownells Niedner that is too small for my use.
Please let me know if you come up with an answer.
Best,
Steve