Just as Thommes DR12-7, my GCR-7 with sideways M is all laminate. I have been lead to beleive that the model coding means GC for "Grand Concert size" and the R is for Rosewood. The 7 is model level, where 7 was one of the highest levels. My sample has a zero fret, but I have seen other GCR-7:s without it, and with sligtly differrent design. Mine does not have any pattern in the midseam of the back, whereas others do.

I have read in Levin brochures from the seventies (Levin Guitars was the Martin and Sigma distributor in Europe in the 70:s)that the Sigmas where bought from several different producers in Japan, which explains why there may be a differrence between instruments with same model code.