What type of diamond plate is this?

[Railroadman]

I'll add this FWIW - back in 1966 Stahl made one rugged heavy duty utility box. I'm trying to cut one section out of that floor and every time it seems all set, there's another weld to be dealt with. No Chinesium in that, just good American steel and pride, and Bubba did not work there. I overloaded the crap out of that truck SO many times back when it was on the road and it just kept asking for more.