With acoustic guitars, the serial number is usually written somewhere in the sound cavity of the guitar. If you want to know the production year of your Yamaha guitar,you can decipher it with the serial number decoder, or find it in explanation about the dating system below.
How can I tell if my Yamaha f310 is real?
You can also check the headstock as it is sometimes not perfect and for sure check the tuners as Yamaha tuner almost always say Yamaha. If all eles fails look at the pickups. These are generally stamped Yamaha or at least have marking on them. Most copies have no markings on the pickups and are just blank on the back.
Can you look up guitar serial numbers?
Checking a guitar's serial number is a good and easy way to validate a guitar. You can look up a serial number either in Gruhn's Guide or run the number in the manufacturer's database.