Please note, I am not the seller and I don´t know the instrument sold on ebay.
In fact, until now I´ve never seen another 55b Crane Duet in real life but my own.
My 55b Crane lachenal is exactly 17 cm across flats.
it's 6.7 inch, slightly more then 6.5 though.
If you open it up, the reed pan is fully stuffed with reeds.
It should be possible (but quite a puzzle) to make a smaller one with the same reeds,
I really doubt if smaller Cranes with the same number of buttons exist.
I am the happy bunny who picked up the 55 button Crane on ebay. I am currently waiting for it to arrive in Australia. I am upgrading from a 48 button Crane Lachenal. I will let you know how it goes when it arrives.