Found this monkey wrench with a jaw that make it look like it would grab a pipe.  I am not sure why there are teeth on the outer side of the jaw.  Maybe the pin can be pressed out the jaw rotated if it get warn.

  Jim

Jim,
      You are correct in your assumption that the pin is removeable and the external jaw may be used to replace the one that is worn out.  Kind of a neat idea.  See the following links for more info:

http://www.datamp.org/patents/displayPatent.php?number=28,487&type=D

http://www.datamp.org/patents/displayPatent.php?number=452,518&type=

Page 330 in Cope shows a picture of your wrench.

Nice find!!!

Mike

Neat idea, they would never consider doing that nowadays though.

Gimme your mullah.

 Very neat wrench. Don't recall seeing one in the wild.

First on I've seen and at $5, hard to pass up.
Jim