I have a client that wants this EXACT FONT, and I can't find it anywhere. Could really use a hand on this one.

Looks to be hand drawn .... from an era when there were no computers.

Def hand drawn/engraved but there are specialists out there recreating fonts from the 'gaslight' era, notably Letterhead Fonts
http://www.letterheadfonts.com/fonts/styles/late1800s.php
http://www.letterheadfonts.com/fonts/styles/early1900s.php
Should be able to find something to please the client if not match the billhead,exactly but at a cost.