See what you mean: the Yamaha Revstar doesn’t have Yamaha on the headstock, but does have the tuning forks.

But other Yamahas don’t have the tuning forks but do say Yamaha. Eg. https://uk.yamaha.com/en/products/musical_instruments/guitars_basses/el_guitars/sg/index.html

I think there was a period, pre Revstar, when motorbikes had the tuning forks but none of the Yamaha guitars did.