http://www.youtube.com/watch?v=d5pc53pYnhs...feature=related
Not a concertina, but worth to take a look.
Shand Morino from Hohner, looks like 90 bass Stradella and 3 row semitone

Okay Misha, you knowing about things like this, how it he switch stops for that one tune without his left had leaving the buttons? Impressive instrument, impressive player. Must have to be one stout lad to drag that thing around though...whew!

He may have levers underneath of the keyboard. And it may have one broad button for master switch too. so slight movement of the palm turns it on.
But I would guess that Theo and Richard Morse know piles more about "things like this"

Morinos are very easy to play. The reeds are very responsive. My Hohner Overture is wa-ay below in quality, and heavy, but it plays wa-ay easier than any 2 rows I had. The only problem "I" have with it: 8 basses instead of 12, and 4 voices instead of 3. It's too heavy and not as universal for world music.

There are couplers on the front of the box. You can clearly see his right index finger poking one of them at around the 59 second mark.