I just picked up a Sigma that someone tried to disguise - they scraped of the headstock logo, blacked out the Sigma stamp on the inside and tore out the label. I can see that it was made in Japan and the serial number is 526649. It's a solid spruce top with a black pick guard and thick white binding with an thinner black/white/black/white/black inside of the thick binding, and the sound hole has a triple ring of black and white. The back and sides are rosewood - I can't tell if it's ply - and the two piece back has what looks like a maple and rosewood checkered inlay. The neck is rosewood with dot fret markers. Any ideas as to what I got or how old it is? I just brought it home and am about to restring it, but even with ancient rusted strings it sounds pretty good.

Thanks for any help you can give.

David