If I remember correctly (which is a big "if", nowadays!) those butterfly banjos came out of Asia in the '80-90's. The (most likely) original, pre-EPA Remo Weather King head points toward that time-frame, also.
Looks well built.....it's got a massive rim on it. Sound & tone will depend on what sort of tone ring is has....Asian die-cast, or an actual sand-cast brass/bronze tone ring.
This is likely a Harmony in name only. By the time frame Scott mentioned, which sounds right to me, I believe Harmony had been out of business for many years. The flange plate seems to be missing. If someone wants this for an old time banjo they could be very disappointed. There are much better designs for old time playing. If the plate comes with the banjo it would make a fairly decent bluegrass banjo.
There is a critical photo missing. A "side shot" at an angle will show whether the flange is present and how it's built. I suppose it might be one of those concoctions where it is attached to the RESONATOR more or less permanently, and the whole rig attaches somehow to the pot.
I wouldn't offer $100 until there were a lot more photos and info. And some way to be sure the neck is straight and attached properly to the pot.
That rim is a 4 piece "block rim", it looks like. Odd.
Not exactly a "Masterclone". At best maybe a $500 instrument?
I had one I bought about 1996, it was FILTHY and looked like it had at least a decade or two of grime on it when I got it. I scrubbed all the metal pats in the sink and the chrome cleaned up nicely. Someone had played the heck out of it and it is possible that it was on the second set of frets when I got it.
Mine was branded "Antares" and had a multi-ply rim. I paid $150 for it and sold it before I moved to New England for $150 (I had not played it in years as I had lost interest in bluegrass shortly after I got it). It was my first "good" banjo.