What kind of material is the OEM EGR Gasket made of??

I went to put in my blocker plate the other day, and when I climbed up on the motor and took at look where it would go, it looks like there is a piece of aluminum already in the spot of where the blocker plate would go.

Is the OEM Gasket Aluminum?? I didn't go ahead and loosen anything up to check it out, because I woulda been pi$$ed if I did all the work and saw there was a blocker already there.

I bought the truck Brand New, so there was no previous owner that could have put it in there.