Zac, welcome to the forum. Did you get a chance to read the FAQ, it has info on black grips?
I am not a 3rd Reich expert by any means; but would expect it to have a aluminum base mag, mostr likely eagle 655 marked and "should" have the serial number on it. Finding this exact number is worse than a needle in a hay stack, and to make one is considered bad form
The grips I would expect to be wood, not sure if walnut is correct, but to tell you the truth I am unsure. And again would be last two of the serial number and marked eagle 655.
If "real" black bakelite grips, they are worth a couple of hundred if in good shape.
Ed