I have a large key-wind François-Charles Lecoultre cylinder music box
(piano-forte with two combs), built around 1840-50, which I purchased
at auction in America about ten years ago.  Sadly, it never came with
an original loose winding key, but I went ahead and purchased it anyway.
When I got it home I had a brass key made for it which does the job of
winding it up and is a tight fit, but it just looks horrible -- modern
looking -- and does not go with the box.

With a vernier gauge I measured across the flats inside the key that
was made and it measures 7.40 mm square, which tells me it is an
Imperial size equivalent in metric.  Does anyone know where I can get
a large, steel French-style clock winding key of this size for this
box, or what style key this box would have come with?  Any help on this
would be much appreciated.

Nicholas Lyles