I was recently talking to someone with a nickle plated frame, it was a Cheney (originally near you Steve at Fleet) they usually made moto-cross and enduro type frames but this was one of six Phil Read had ordered specifically to build a batch of Yamaha twin engined GP road race bikes.
Anyway, the nickle plating comes about because the frames were made from thin wall high spec steel tubing that was joined with a high nickle content bronze brazing rods to best match the steel's toneage rating. apparently if you chromed this combination, then there would be a transfer of chromium into the nickle joints that would degrade their strength rating.......so they are usually nickle plated to avoid this, it's also very thin and light weight while offering goog corosion resistance.
All that I guess has nothing to do with a Honda frame, the Read/Cheney/Yam was really nice though.
