This is one of the more unusual markers I have seen.
It is made of a heavy metal, bronze perhaps. There
are three identical facets on the other side. That
makes six equilateral triangles plus the base.
A mason.
Strange shape. You're right about that. I always wanted to show the names on my grave photos but was scared they would come after me.
Apparently this has been autographed like your birdbath and it looks like the same writer.