Should be in their book, and pretty much broadcast webwide, as for the M use, the size, etc. Lacking the book, anyone is free to correct, but Behring was saying same on knives he has sold, if you google Ruana model numbers and Treeman.

As for dating, they mainly use the book and Vic's memory at the shop. There is a newer book out now, which may correct things. But generally, if a small M, that 20yr range is best anyone can do. I read of one guy asking about a rough one, and him saying he was told maybe in the 70s when Rudy's eyes starting to go, which is pretty vague. Rudy had various family members (including grandsons from sons) in and out, but Vic and his grandsons on that side apparently were the ones who stuck with it in that shop, and ended up with rights to the shop and name.