I have a Yamaha FG-230 12-string acoustic guitar. It's got a red label in the sound hole that says "Nippon Gakki," which is what Yamaha used to be called. I wanted to know more about it, and the Yamaha online guitar serial number finder had no info on it, so I e-mailed them (guitarguru at yamaha.com). They told me it was made sometime in 1968-1972, and it has a spruce top, mahogany back/neck/sides, with a rosewood fretboard.
It's not worth much, apparently. $200 tops, judging by eBay, but even then, mine's not in very good condition. It's got some warping on the neck, I think.
This was my first acoustic guitar, and I had it strung as a 6-string, and I loved the booming sound. I think I'll hold on to it and someday fix it up, bring it back to life. Maybe I'll bring it in to my local music store (Bigfoot Music) and see what they have to say about it.
Speaking of Bigfoot, I need to buy a ukulele from them for Christmas, for the kids. And maybe a book so I can learn to play it.