Coming back to the question of date, it seems that the Baltimore Overall Manufacturing Company had gone bust by 1913. They were the subject of an adjudication on 24th June 1913 relating to payment of a dividend to a stakeholder while in receivership, in which it was stated that they were “an insolvent corporation and now in the hands of receivers, appointed by the Circuit Court of Baltimore City, to administer and wind up its affairs, under the supervision of that Court.”
The Southern Overall Company must have been in existence before that since there are trademark applications by the company from at least as early as 7th February 1911. Perhaps they bought out the remaining assets and trademarks of the Baltimore Overall Manufacturing Company in 1913.