a diamond flathead block

[Walt Dupont--Me.]

I can't remember ever seeing diamond flathead block. I've seen diamond Model B blocks, I have 3 of those blocks. I'm building 41 engine right now out of a vergin 41 coupe with 43 original miles on it. After having the engine baked out and shot peened I had the engine upside down on my stand and see a diamond between the water drain hole and the pan rail. How many of you guy have seen one of these? Thanks Walt