Yamaha’s serial number system is one of the more complicated ones I have come across – so it’s a little bit involved.
But the complexity of decoding the number isn’t the most frustrating part of this particular serial number system – it’s the fact that the serial numbers actually repeat every decade – so you actually have to know what decade your guitar was built in to begin with.
Dating yamaha guitars serial number
I just wanted to clarify one point: since you say you can't find the model number written anywhere, maybe it would be helpful if we could try to reach a consensus on what it says.
To me it looks like "GX-3000" but I could maybe see a "GV" or "2000" in there, so I'd be curious to know if other people are seeing something I'm not.
That's a lower case "F" as written in cursive (almost exactly how I would actually write it) and I think the character after that is an "X" but where the crossing of each stroke is so low it's almost a "V". 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.
The only GX guitar I know of from Yamaha is the GX-1 which is a headless electric model and therefore not what you have.