Waltham watch Co. Marked Model 1857's of this Gen II type were produced at least in the Range of 441,001-443,000 from December 1869 to March 1870. I would not be at all surprised that this could have been in that run but not serialized. Possibly a "Snatch", or setup movement. The American (Waltham) watch Co. factory leaked watches like a sieve in those days.
A glimpse of the rest of the parts for a possible serial number could help track it better.
Posts: 6492 | Location: Southern California in the USA | Registered: July 19, 2007