As an owner of a 52SGCS-6 since 1984,purchased as a used model I am always interested to see comment regarding this lesser discussed model.I absolutely treasure mine and of the 7 playable guitars currently in my collection the sigma I would play more than 90% of playing time.I never realised back in 1984 just how good a guitar I was getting for that $110,it seems to just sound better and better and the action is simply excellent.I recently purchased another Japan built circa 1983 Sigma DK28 12 string with Martin thinline p/u installed from the original owner in New Zealand which I have to collect sometime along with a 1983 Tokai CE320.Playing time will have to be shared with these 2 when I get them home.I always thought that the 6 indicated 6 strings now I have seen 4 and 7 so now am aware that this is likely a reference to model updates.I read that the 4 has no neck trussrod.My 6 definitely does and adjustment is via coverplate on headstock.Headstock has the sigma symbol abalone/paua inlay some refer to as the sideways M with the gold stamp "SIGMA" across the face.ID is by way of paper sticker in body and has no serial numbers.