This is some information on your Yamaha GC7 from the Yamaha Guitarchive web site.
Year(s) Sold: 1979-85
Original MSRP(US$): $850.00
Top: Solid Pine
Back / Sides: Rosewood
Body Depth: 89-95mm
String Length: 650mm
Nut Width: 52mm (62@12th fret)
Notes: Hand Crafted
It is difficult to suggest a value without looking at some photos on the condition of your guitar.
Recently, there was a GC5M listed in the big bay auction site, asking for about $800.00 with everything original, including the luthier signature on label and the Yamaha case. The seller is from Japan. The auction was suddenly stopped. Perhaps it was sold locally or directly in Japan.
Yamaha GC series from the 70's seemed to gather a bit more following than those in the 80's.
I am no authority on Yamaha guitar values.
The following suggestions are just what I have observed in the market.
Price it below $1,000, it may go quickly depending on how much below $1,000.
Price it between $1,000 to $2,000, it may stay in the market for a while. Whether it will sell depends a lot on the conditions of the guitar.
Price it above $2,000, it will have to wait a while for the right buyer to come along.
I still would like to see some photos of your guitar.
Last edited by waikuentsui on Mon Apr 28, 2014 5:16 am, edited 1 time in total.