It's @4-1/4" long.  I thumbed through both Cope 1830-1915, and Schulz's, and couldn't find it.

Looks like a mark on the body. Can't make it out at all?

I looped it and couldn't make out anything.

Could be a GEM by Tower & Lyon, but I don't see one like it in the pictures of GEM and T&L that I see.

I though it may be made by Whitman & Barnes or Speirs & Co.

Peck, Stow & Wilcox made a similar design called the STAR Bicycle Wrench in 1897 (see pg. 11, June 1995 MVWC Newsletter for a copy from IRON AGE) , but it was an open "skeleton" handle all the way, not closed in between the fixed jaw & adjusting nut.  Are there any marks on the shank of the movable jaw?

Nothing on the shank either.  Here's an open pic.