On the top of the bedplate, the 350 means a three tunes, 50-note
movement. Of the numbers on the bottom of the bedplate, one of them
(probably the lower one) is the 'movement or stock number', which
tells someone with a list of movements what tunes are pinned on the
cylinder.

Nancy Fratti - Nancy Fratti Music Boxes
Canastota, New York, USA
http://www.nancyfrattimusicboxes.com/