This is pretty neat, and according to the patent info. the hammer head is replaceable.
This one has;
Union- pat oct.25,1887- 5- 15- unionmade- on it.
First one of these I have come across.
http://www.datamp.org/patents/displayPatent.php?pn=372246&id=39269

Cool! Looks to be in very nice condition too.

Funny thing about that patent. I have a couple of J. Knell lasting pliers, patented Mar 13, 1888. One of the features mentioned in the patent text is the replaceable hammer head. And the really odd thing is, one of them is stamped WHITCHER





It's curious that the same firm would produce two different designs that each accomplished pretty much the same thing.

Kinda like metric bolts eh?!?

>two different designs

It is possible there was enough preference by buyers for one design or the other to justify making 2 different versions of what is essentially the same tool...

It is unusual (to me at least) to see these well marked...

(I assume Frank W. Whitcher, Boston, Apparently jobbers to the shoe trade)

PS: See also patent 1067033