Bob Bolton, I suspect the Sally Army bought and played all sorts of concertinas, in England anyway. certainly my English-system Lachenal is ex-Sally Army, it had the label, -Salvationist Publishing Co,- and it had even been recently retuned from the sharp pitch they used.
Brave, to start with a Duet. There was a guy with one arm who used to play one, half of one anyway, very competently, years ago, in a group called (I think) Swan Arcade.