The 0 is just a factory assembler's mark. The missing rework date is not unusual for certain periods, nothing is ever completely consistent on S&Ws.

The import stamp can mean it just left the country and could have gone anywhere in the world and imported back into the USA. With the importer being in VT, it may have been purchased here by an individual and carried or sent to Canada, then imported back from Canada.

A letter may be helpful, especially if it was shipped out of the country or to an exporter in the USA. Letters usually show the shipping destination, but won't have any import information.

__________________
Jim
S&WCA #819