Yamaha numbers are very confusing from that era. I've seen guy's turn up for the pre70 class on a bike that has an RT1 engine number only to be turned away as they have an RT2 or 3 reed valve motor. Their not all that happy as they bought the bike as a pre70 eligible machine. Some have fitted piston port barrels and raced them in pre 70 but the piston port RT1 barrel are like rocking horse poo.
I would have been happy to buy it but as I'm in Brisbane I have no way of picking it up and I hope the other guy still wants it.
The pipe is an RT2/3 or DT2/3 pipe with a TS250 heat shield fitted, every thing else is original except the front guard