Pocket Watch Database
"2123" could possibly indicate the grade of the watch and not the serial number of your movement. Serial numbers are usually more than a few digits.
Due to the lack of existing factory records, our U.S. Watch Co. (Marion, NJ) database has been reconstructed using observations of known watches.
As a result, the information may contain inaccuracies. Please let us know if you have details that can improve the database.
From the American Horology Archive:
United States Watch Co. (Marion)
Grade: Fayette Stratton
Mixed Run: 15-Jewel and 17Jewel Movements, Gold Balance Screws
|Manufacturer:||U.S. Watch Co. (Marion, NJ)|
|Manufacturer Location:||Marion, New Jersey|
|Movement Serial Number:||2123|
|Estimated Production Year:||1867|
|Movement Markings:||Fayette Straton
Mch 13th 66
Research Note: Mixed Setting Types In Run: KS/BS/LS