Jaw covers are pretty common. What's the material for that? From here, it looks like copper, a fairly common material among machinists.
Clever idea.
Oh, and congrats: nice vise. I've got a similar Prentiss Bulldog vise, that came with the rare "really rusty" option. I need to clean it up and put it on the bench. Soon. Sometime. While I can still remember what a vise is for.