Lyman C. Smith himself in Syracuse, N.Y. hired the best engravers to engrave his guns. The best at the time were A.E. Spangler, his brother Wilton and Jacob Glahn.
Spanglers' dogs are some of the best done.
The snipe pictures and the trigger guard engravings look like Jacob Glahn.
When L.C. sold the gun works to John Hunter in 1899, the Spanglers and Jacob Glahn and his three sons went to Fulton. His sons then went on to engrave for others.
I have seen Spangler's name on an Optimus Grade and Glahn's on another LeFever.
These engravers also worked on the side for other gun companies as you have stated.
Jacob Glahn
A.E. Spangler Optimus Grade 10 ga. presented to President Benjamin Harrison
A3 L.C. Smith, most likely Spangler.
Forgot to add this Quality 7 Syracuse L.C. Smith circa 1887. Most likely Spangler.
