Excellent bike. It looks all original but it must have had new paint at least. The seat is the only thing wrong. I had one exactly like this in my teens and it's my fave of all time. The gear shift took getting used to cos neutral was at the bottom. I loved the noise too; induction howl and straight cut gears. Love it.
Had one new, in1972, followed, by 750 triumph triple, then another mach 3, (H1B) also had 350 triple (S2)nice.. Favourite was H1B, but I think the 400, s3, was probably the best sorted of them all, rode one but never owned one! Still have soft spot for the triples!!! 🇬🇧