My strange clarinet

Hello people! Here are some pictures of my old clarinet. It's a wooden one, and it's a Normandy model. But I coudn't find any information about this specific model up to now. The guy who sold this to me told me it is about 80 years old. It's a Bb clarinet, but unlike the other clarinets I've seen around, this one has all its keys closed, a mechanism that resembles more a blass clarinet than a normal clarinet... Another weirds things: it is all in one wood piece! You can't separate it in two parts in the middle, as usual. Old design? If you have any information about this particular model (when was this kind of model made, why its mechanism is different, and so on...), please feel free to write!