Never been ridden 70's gordon and smith single

Ok, at work about a week ago, i noticed on the bulletin board a guy selling " 1970’s single fin never been ridden ". Obviously i was curious, and emailed him. He told me that someone back in the 70’s had stolen the board, but was not a surfer, so the board was stored and forgotten. The guy who posted the message ended up with the board around 15 years ago, and has had it since. Not long ago, one of his mates told him about old boards on ebay. So now he wants to sell it. I asked for pics but got no reply. Would anyone have a rough idea of what this would be worth??, IF this guy is telling the truth haha. It’s 6’4’'. I think he’s gunna put it on ebay, but im not 100% sure.