Some HO model, perhaps a Sunshine, did have hatch covers formed of diamond plate, and a photo accompanied it to prove that this was correct.

But I would note that this plate was probably 1/8" thick at best, so it wouldn't be that heavy.  As far as I know, diamond plate, also known as diamond tread plate or checker plate, was and is never very thick.  It's advertised currently as 1/8" and 3/16" thick, and I doubt it could easily be rolled much thicker.

Ron Merrick