This maybe trivial but it is somewhat the one thing about bricks I do know about...and it's that the maker of your Imperial Steele brick was based in Haldeman Ky, not HaldeRman. I grew up there and the added R sort of a matter of contention with a lot of people there.
The Kentucky Firebrick Company also made bricks that were stamped HALDEMAN. I had a lot of family work there and I have some bricks I'm going to turn into an outdoor stove. I can direct you to where you can get some of those bricks if you like.