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. Attachment 278024Attachment 278025Attachment 278026
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!

All the vintage ones I bought were all BBWs, some looked like slate, but after lapping it unveiled sweet looking BBWs
I noticed that BBW sides weres sometimes heavily used, and I love using them as well

There's a TON of different BBW types, they're gorgeous stones if you ask me

1st stone looks like a synthetic coticule to me, 2nd is just bbw, some look that way

yep, what kcb said, it's a bbw backing. Some just look like they have larger crystals in them than others... especially vintage ones. In my experience the ones that look like that generate a much more reddish slurry than most of the ones being produced today. unsure why that is, but that's just been my experience. most definitely a bbw though

Interesting thank you gentleman!