[HO LEMANS]

I was in the process of disassembling the rear axle for my 350 H.O. Lemans so JD race can work their magic on the Posi unit and when I pulled the bolts for the bearing caps I was surprised to see that they are copper.... is that normal?
I have never taken one apart that hasn't previously been messed with so I don't know and figured someone on here would.... I am assuming these are a one time use bolt as well?

thanks

H.O.