A simple magnet will tell the difference and when I got the bicycle it got the original sticker noting stainless frame bicycle. I got a lot of stainless bicycle parts and can identify stainless steel from pure stainless. A simple way is applying metal polish. Stainless steel when polish shows traces of black residue on the cloth used. My brother do have an original Japanese bicycle with stainless frame and fork also. Will try to post it later.