I'm a bit puzzled by the specs too.. Found this, one of several positing black dots from iron during production.I noticed the black specs because I thought it was dirt… then noticed more and more. Maybe the Collectors Cage will have some insight.
Thank you for your reply 😊

Black spots inside leather
I recently got some untreated veg tan, half a shoulder, and I've used about half of it without issue. Last night though, I noticed a lot of black spots appeared after skiving. Today I cased a piece, and now there's black spots on the surface as well. Heres some pictures. Sorry about using imgur, ...