Not Banjo-Zithers but...

I'd seen them in pawn shops and the occasional music story. I saw one in a shop in Perth, Australia and figured somebody had decided to build a banjo from seeing one once in a picture, decades earlier. I didn't notice that the ones I saw shared common features. Had no idea they'd once been considered a superior design of banjo. I always thought they were made by people who just didn't know what they were doing, primarily because they always featured a six-peg peghead for a five-string instrument.

(Mind you, there was always this sophisticated re-routing of the 5th-string up through the inside of the neck to pop out in the peghead so it could be looped with the rest of the strings, instead of having to dig a hole in the side of the neck for the 5th string peg, but I was still flummoxed by that unnecessary 6th peg.)

Turns out the 6th peg was included to provide symmetry, as in the picture below. Nobody wanted a peghead with three pegs on one side and two on the other. Or two on each side plus one lonely stub halfway down the neck. Perhaps that isolated peg reminded the banjo-plucking sailors of the unpleasant possibility of being alone in a lifesbuoy, bobbing up and down on the high seas...



Here's a fansite, including an essay-length answer to the immortal question, What is a Zither-Banjo? It also addresses the fascinating question of the split second-fret, another unique feature of the instrument.

And here's a definition from a brief UK Banjo dictionary that is itself worth a look, if only to tell you the difference between a zither-banjo and a banjo-zither, though there are other things there that you might need to know.

"The zither banjo became popular towards the end of the 19th century. Usually 5 string (often with 6 tuners). Typically  featuring an a wooden resonator encompassing a cast metal pot, and no perch pole. The 5th string usually was diverted through a metal tube under the fret board from the 5th fret to the tuning head. Considered a superior design of banjo at the time. Examples of 6 string, 7 string, tenor and mandolin banjo also made."