I've got a 48 with Crane & Sons label which looks a lot like yours - Lachenal serial no 256 on the insides. The right hand bar, which carries the Lachenal trade mark, also has a second number impressed into the wood - C & S 844, which I assume is a Crane & Sons number. However, my other Crane, a 56 'New Model', which a Lachenal-badged with serial number 693, also carries a 'C & S' number, partly obscured now by wear, which appears to have been 'C & S 08809'. I don't really know what is going on there, and I suspect no-one else does these days either.
Interesting!Comparison with my own Crane & Sons instrument tells me that we have a topic here which deserves more focused attention, so rather than continue to hide the discussion here, I've started a new Topic in the Concertina History subForum.
Please join me there.