La Veinette is almost always a natural combo, because the layer is so thin that they can only cut one slice from it.
Only in the rare case that the Coticule separates from the blue stone and that blue stone is scattered, they'll glue it to slate.
That said, if you compare the side view of n°53 with yours, you'll see an almost striking resemblance.
We've had several confusing layer determinations lately. I don't know who wrote LV on that stone. Could have been someone at the SuperiorShave, or someone at Ardennes.
But regardless of who wrote those two letters "LV", and what he meant with them, I can only share what I think it is, based on what (little) I understand about the morphology of Coticules.
If I'm correct, you have a fast Coticule, that will provide a lot of tactile and auditive feedback while in use. The slurry should start to discolor almost immediately when you make halfstrokes, and the feel is that a a very fine, but quite present abrasion. That abrasion will not completely disappear as you progress to clear water, as it would on some other layers that turn "glassy" when working on water only.
There is a high chance that this Coticule is (relatively) fast on water. That means that you will see traces of black appear in the water after one set of halfstrokes starting on clear water.
That is the information I predict upon seeing this particular stone. What someone calls it, is not all that important.
Kind regards,
Bart.