There is an LC Smith lockplate engraving in Col. Bropy's book clearly signed Glahn, in the section about engraving. If you haven't seen those photos, let me know and I can scan them (many others here have the book too). Only Jacob Glahn and Albert Krause are mentioned by Brophy.
It's interesting too that your ancestor didn't come to Fulton until 1893. There's a bit of uncertainty about how long the Syracuse factory continued operating while Fulton was setting-up and there is serial number confusion during that period too. I've always suspected that they continued to produce hammer guns in Syracuse for gov't contracts during that time in spite of the relocation. If engravers were still working in Syracuse however they must've been making some sporting guns there then too.
Thanks for sharing a little bit of your family history. Many times little details explain a lot.