The patient:
A 1890's Henry L. Mason Parlor Guitar
The problem:
I refretted it, replaced the broken bridge, and undertook a few minor crack repairs. Now after stringing and setting it up, it is buzzing in spots. Not quite a regular fret buzz.. something more sinister, more hidden. After spending the good portion of my evening trying to locate the buzz, I resigned myself to releveling the frets. Surely this'll do the trick, I thought.. but alas.. the buzz remained. After another cup of coffee, and some head scratching and cursing, I found it. The back buzz as called by ol' Mr. Ford himself. The string rattles against the fret(s) behind the fingered fret position because of a nut that is slightly too low. In this case the buzz is only from one string so rather than shim up the nut as suggested by Frank, I opted to add a bit of dust and CA to the slot and refile it slightly higher than before. (it's the original ebony nut). Problem solved!
There is a post on "back buzz" on frets.com, but I decided to post this here just in case it saves some poor soul from a long night of chasing a buzz.
Long Live Frank Ford!
Viva Frets!