Anyone ever see another hammer like this? This was a first for me! Handle doesn't go through the head, the head is solid on top & bolts onto handle.

First for me 2

 looking at the style of washer and bolt, I would say that they are a replacement for the original fastener.

I have an old hammer like that, but it looks like a rivet, not a bolt.

Strap hammer. Our member Scott Grandstaff makes some outstanding examples.
http://users.snowcrest.net/kitty/sgrandstaff/

Only ones I've seen are the ones Scott made. First hammer I've seen where the handle doesn't go through the head , other than one piece steel handle types.
Probably designed to protect the handle.

I saw an unusual hammer much like that one this am.  Larger, though.  One head suited for pounding railroad spikes; the other was a pickaxe.  And the tabs were front and back, rather than side and side.  The handle would fit into a 3/4" recess.
I never saw one like it before, but I can see that it could be useful if rookies were missing the spike as often as hitting it.

I've seen drawings, but never even pictures except here.  It was, as I understand it, one of the attempts to solve the problem of handles snapping off while pulling nails, more or less overcome by the Maydole adze eye design until recent years, when some of the old ideas have been resurrected in new forms.

i had a similar one,with the straps on the top/bottom,.not sides