You might want to try the Kramer Owners club here on TB. Might be a little hard to find; don't recall anyone posting lately, but it's around here somewhere. You might also try www.vintagekramers.com
. There might be useful stuff there. I have 3 of them; all older than yours, though. Kramer serial numbers are, sad to say, not very useful, and Kramer was famous for changing things in the middle of the stream "just because". 2 of mine don't quite
fit the printed description of them; but they're Kramers, soo....
If it sounds good, and feels good, I really wouldn't worry about it. Just enjoy, and play the snot out of it. IMO, Kramer has never made a bad bass; most people don't know what they're missing.