hi there...
my information re: dating the lachenal came from this page of Don Nichols... : Click here
There was also a page describing the crane system which i can't seem to access right now.... He does have quite an extensive page on concertina's.... and a listing of serial #'s and dates for Wheatstone, and formulas for Lachenal's for dating the instruments.. worth checking out.
RE: the SA and the concertina.. my wheatstone is actually an old SA instrument... my grandfather was SA, and so was his family before.....(Mine too for a while.) I could possibly find out more about that aspect if you were interested.... (may anyway.....)
musicman