A few reasons I say this:
- In my experience, the biggest strength of Yamaha musical instruments is consistency -- to see something that looks handwritten is a pretty big red flag.
- You haven't mentioned a serial number at all. I assume that if there was one, you would include it. One aspect of that consistency is that every single genuine Yamaha instrument will have a serial number, with which one could trace the instrument's origins. If it's missing by design, the instrument is not genuine.
- I did a google image search to compare your image with ones of genuine instruments. The design of the sticker inside the sound hole varies with the time period, but I noticed the following qualities that are present in ALL of those versions, even back many decades:
- The model number is always CLEARLY displayed in big block letters, often larger than the Yamaha logo itself.
- The sticker inside the sound hole is almost always the same shape as the border. For example, if the border is oval or rounded rectangular, the whole sticker is the same shape. Your image showing a rounded border but a rectangular sticker seems to be pretty anomalous.
Here's the closest example I could find: a Yamaha FG-402. The sticker pattern has the same kind of border as the one you posted, but the sticker itself is shaped to the border instead of rectangular.
This image also clearly shows where you would find the serial number.
It also brings up something else. See the language used on the sticker in that picture:
Made by Kaohsiung Yamaha Co., Ltd.
in Taiwan in accordance with specifications of
Whereas your sticker appears to say:
Made in Japan
in accordance with specification of
Typos are a HUGE indicator for counterfeit merchandise.
After quickly looking over the other imagery you provided, I think the logo on the headstock in particular is quite suspect. I believe the "YAMAHA" wordmark is not in the correct typeface. If you compare it to the inside sticker (which in your case is probably a photocopy), the middle stems of the letter "M" are not supposed to meet the baseline in the proper wordmark, but on your headstock it does appear to. Also the other letters ("Y" in particular) look too wide to me. Every other genuine Yamaha guitar you ever see will have the same exact wordmark, in the exact same typeface.