Working on cleaning my seats and a plastic-like substance was
coming off one section. I'm wondering if it is original top-
coating (like more modern seats) or if it was a repair of
some sort done by a previous owner?

I think it must be a repair job. The seat in my '94 is worn on one side and I don't have anything like that going on.

Guess I should also confirm that the top of the side bolster is in fact leather. I know (or at least I think I know) that the sides and back are ambla/vinyl.

From another website I'm wondering if there's any leather on my US spec 4 liter aside from (confusingly) the back seat. ?????

Rich Connolly plastic just doesn't have the same ring to it. I'm going to have to go look now.

Before you get too worried about it, apparently the V12's got full leather - and I mean full.

I didn't realize there was a difference in the interiors. Was going to say it looks like leather to me.