Indeed, that's a vintage Coticule, glued to a BBW.
It looks like the "La Grosse Blanche" layer, which is very easy to recognize throughout all former mining sites, because it's the only one that oxidizes to a darker color. If you rub the stone a bit with a slurry stone, and fresh pale Coticule emerges, you can be sure it's a La Grosse Blanche. Fast and fine. Offers among the mellowest edges.
The crack may be a bit of a problem, but it runs in a good direction, so the razor won't catch it. If it shows any sign of separation, impregnate it with CA-glue. wipe the excess off before it cures. Lap the surface afterwards.
There's a traditional way to fix this issue as well, but it's a lot more hassle. You need to melt hide glue and beeswax (50/50). Than heat the hone in a skillet and till the filler starts running into the crack. Don't touch the hone while you do it, because the glue used to bond the BBW to the Coticule is the same.
Kind regards,
Bart.