Got my GCR-7 Serial # 73010988 "a rosewood 000-21 clone" for $75 from a friend back in 1988. The paper lable is still very readable, and the "M" above SIGMA on the headstock is pearl. There's a black plastic white edged truss rod access cover above the nut. Although not real loud, it's a wonderful sounding guitar with a very comfortable shape. It's been my beater for all these years, but differs from some 000 Martin attributes. Some exceptions are the adjustable saddle, and a 14 frets clear, modified-V neck profile with a 1 11/16" nut (like an OM-21V?).

Based on the GCS-6 post above, I wonder if the first two digits of the serial number could be the year it was made? Thanks for the information, it's cool to finally find some good Sigma info, especially to learn it's one of the "most desirable vintage Sigmas".

Thanks,
JJ