I tried the serial number thing at the Yamaha site also. Got the same results that you did. I am sure that you saw the phone number that you could call: "If the Wizard still indicates an "Invalid Serial Number" contact Yamaha Customer Support at: (714) 522 9000."
Found some Yamaha 12-string ones for sale on Ebay. The prices varied greatly. You might find one comparable to yours there. eBay - 12 string items on eBay.com (http://instruments.search.ebay.com/12-string_Yamaha_W0QQfsooZ2QQfsopZ2QQsacatZ33033) eBay: Yamaha 12 String Acoustic Guitar FG-312II NO RESERVE!!! (item 190072818605 end time Jan-25-07 09:25:16 PST) (http://cgi.ebay.com/Yamaha-12-String-Acoustic-Guitar-FG-312II-NO-RESERVE_W0QQitemZ190072818605QQihZ009QQcategoryZ33 033QQcmdZViewItem)
I also found the following add on Craigslist for Atlanta, Georgia
It is not a 12-string one. But, contents in the ad may be of use to you.
Yamaha FG 300A Acoustic Guitar-LOTS of pics - $75
--------------------------------------------------------------------------------
Reply to:
[email protected]
Date: 2007-03-31, 3:48PM EDT
This is a Yamaha FG-300A acoustic guitar. Since Yamaha doesn't use a serial number system, establishing a date of construction for this guitar is impossible, but I would guess that it's approximately 15 years old. Given its age, the guitar is in remarkably good shape. Except for two paint chips (pictured below) and a bit of very slight wear here and there, this guitar has aged very well. The nut, machine heads, bridge and frets show very little, if any wear at all. Also, the action on the guitar is very good, especially considering that it's probably never been serviced by a luthier, and the intonation is better than on my Gibson SG.
Even though this is a comparatively "low cost" instrument, it's not a cheapie. Yamaha makes very decent guitars–especially considering the instruments' costs.
This would be a great first guitar for someone to learn on without paying through the nose on a higher cost instrument, or an extra guitar for someone looking to complement their collection. I simply don't need this guitar, and I have too many already. Got to thin the herd.
Comes with a hardshell case.