Here's an interesting thought I came up with this morning.
Unfortunately I didn't pay attention when you mentioned any maker's
marks on the hammer, they'd have easily proven or disproven this wild
theory.

How about a piton hammer?

For those of you not crazy enough to climb up sheer rock faces, this
is a galootish tool used for driving pitons (essentially big iron,
steel, or rarely aluminum nails of various shapes) into cracks in a
rock wall, as protection from falls while rock climbing.  The practice
of using pitons has fallen into disfavor except under certain
circumstances in certain locations.  It did a real good job of
destroying the rock.

If there's a maker's mark with a C in a diamond, then I'm sure you've
got a piton hammer.  Otherwise, heck, it was worth a try.

Alan