Would anyone have a ballpark idea of what an approx value of an early 70's SG would be? A guys I work with got it for his 14th birthday back in 1972, and it's been sitting in it's case ever since. He said that it's in almost new condition, it's just been set us and has no neck issues or anything like that. He's not looking to sell it, he just gave it to his 13 year old son. Any ideas?