It does sound like you have a "Strange One" on your hands, at first I thought it might have been a SG Special that someone had messed with, but you say it has the block inlays in the fretboard and the ser# is for 74-75, so that rules that out, someone has definitely messed around with it though. Have you ever had the pickguard off? I am wondering about the P-90?, by the fretboard, and I agree with James, someone must have replaced the bridge p/u with something weird, SG's are normally bright and piercing, I think if you are not worried about any collector value, then a decent set of humbuckers is in your future and would have to improve your sound tremendously, by the way, if you remove the pickguard there should be cavity where a full sized humbucker once lived, good luck and keep us posted, you have caught my curiousity with this guitar

[Edited by pstring on 01-20-2002 at 10:28 AM]