Thread: Coticule backers.

I’m curious of the different stones they use for coticules. Up until this weekend most that I’ve seen and all of the ones I have are backed with bbw. I know they use a type of slate these days. What sparked my interest is a couple of hones I saw on eBay this weekend.
The first stone is on its way to me. It appears to be slate.
The second is the really interesting one. It almost looks like a Tam, but the spots seem darker like granite. Has anyone ever seen this? Also is there a time frame they switched to slate or was it just what they had on hand? I ask because the stone that’s on its way to me is out of a barbers collection from the 40s. Thank you all in advance for your knowledge!