I've continued looking around the site. Lots of examples of engraving. I found this german patternbook (Musterblätter enthaltend die anwendbarsten Jagdstücke u. Arabesken für Büchsenschäfter, Graveure etc.) particularly noteworthy: Patternbook of Engraved Designs for Firearms Ornament)
I stumbled across The Metropolitan Museum of Art website recently, and found a pretty good collection of photos of engraved firearms. Additionally, L.D. Nimschke's Scrapbook is included with nice zoomable images. Thought I'd post it here for those studying like me.
L.D. Nimschke's Scrapbook