Probably closer, but I still doubt it. Factory work was notoriously brutal. Figures for calories burnt from sitting vs. standing varies between 20 and 80 cal/h

Probably closer, but I still doubt it. Factory work was notoriously brutal. Figures for calories burnt from sitting vs. standing varies between 20 and 80 cal/hour. 80cal/hr would be substanial over a workday (800cal, assuming factory work was 10 hour days in the 50s...), but 20 would not... If we assume it's ~50cal/hr, standing alone could add up to 500cal difference for a 10 hour day, not even including additional physical exercise from the job itself. Add to this the amount of walking that was likely substanially more common in the 50s, and it sure seems like you could chalk up a 1000+ cal difference pretty quickly.