Ingot Markings

[RG1911]

There's an ad for what look like foundry cast ingots, but the seller doesn't know what the composition is. He just says it's hard, and that some have an "H" cast into the surface, and others have "AAA Alloys" cast into the surface.

An online search didn't yield any useful results.

Is anyone familiar with either mark?

Thank you,
Richard