Wha? You're wiser than me for sure. Never heard of this, just looks like a low Eb. Are you talking about all the alternative thumb key configurations that correct for the octave/Bb key? My bass clarinet has a version of that (i.e. 2 thumb keys, one for Bb, the other for an octave key).
But nonetheless, that's a boehm clarinet surely.
Wisdom has nothing to do with it. With all the variations I saw when I switched to German system, and having a curious mind by nature, I started studying all the different configurations, and what they do.
Yes, that's a Boehm clarinet
. It's a Tosca, one of Buffet's newer high-end models.
No, it's not an alternative register key. You won't notice, because over the years you've learned to correct for it with your embouchure without needing to think about it, but one of the perennial problems for clarinet
makers is the tendency of the twellth to be too wide near the end of the bore. The usual preference is to make the clarion register play in tune, which makes the low E and F a little flat. The correction key opens a small vent either on, or in the case of the Tosca, right next to, the bell to raise the pitch of those notes slightly.