I have an E Thomas Jr(Chicago) which has "J SIMON" on the bar
on the action flats between the barrell lump slots. Gun has
similiar scroll engraving as the Boxlock pictured.

James Donn (Peoria)hammergun-pictured posted recently has
"W F K" on the action flat bar. GUNSMITHS OF ILLINOIS has
in it's Donn write-up that a Scotish Gunmaker named Walter
Kinnser worked with Donn.

On a Nichols& Lefever seen :"A A" is on the action flat bar

Could these be the initials of the primary maker of the gun?
Thanks
Bill

J W McPhail