:recently a friend of mine who (never played guitar)was given an old Gibson acoustic, on the inside there is no sticker indicating the model of guitar only a stamped on letter b and number 15 (b15) i searched the internet and found little info on this model, i DID find out that its a all mahogoney guitar that hasent been made since 1969. I was wondering if you could give me a rough estimate of its value in dollars. thanks