Never seen anything like this. How common are they? Would love to hear one. With that large rosewood section looks like it could be a tone machine. Then again, if it was they might have continued making them.
...without cracks around tone holes. (They are also made as bass clarinets.) Maybe this guy played it regularly and stored it carefully, but most likely it was a closet queen, has dried out over the years, and needs some repair work.
If you buy it, make sure that you have return privileges. Oh, and don't plan on playing in a octavin choir any time soon.
With music and drama a life-long interest, [Jeff] Britting has scored thirteen stage works, five films (two features and three shorts) and has composed various instrumental and vocal works, including Sonatina for Octavin, commissioned by Franklin H. Stover, composer and American rare instrument specialist
The instrument is an Octavin. It's been discussed several times, which you can find with a search on that word. It was an attempt to make a clarinet that overblew at the octave instead of the twelfth by using only a very slightly conical bore. I tried one many years ago. Here's what I wrote in an earlier thread:
The clarinet always vibrates as a closed tube. I have read (in Benade, I believe) that the clarinet reed spends more time sealed against the lay than it does open. This longer time spent closed promotes the closed-tube mode, which is why the clarinet sounds as it does and overblows at the twelfth. During the time the reed is open, the vibration remains in closed-tube mode, since any open-tube vibration is overpowered by the longer-lasting closed tube vibration.
An instrument can produce a stable tone only when it reliably acts as a closed or open pipe. The clarinet is designed to stay firmly in the closed-tube mode, just as the saxophone is designed to stay firmly in open-tube mode. A sax reed seals completely against the mouthpiece just as it does on the clarinet, but for a shorter time.
There have been attempts at an intermediate instrument, with a slightly conical bore that balances the open and closed periods, or falls just barely on the open tube side, but they were unsuccessful. A number of years ago, at the late, great Ponte's music store, Charlie Ponte brought out an early 20th century instrument called "Octavin," which had a clarinet setup but a bore just conical enough to act as an open tube and overblow at the octave. It was difficult to play, and sounded more like a saxophone than a clarinet. When I tried to make a clarinet sound, it quit playing altogether.
Octavins appear on eBay several times a year, usually priced at over $1000. They're uncommon, because they were unsuccessful, and little or no music was written for them. If you bought one, it would be as a collector's item, and to astonish your friends, and not because you might find a way to perform on it.