Nice meeting you yesterday !
The Gallagher Maufacturing Company at 78 Sagamore Street in Lynn, MA was established by Bernard Gallagher sometime in the 1880's, and oringinally made automated equipment for the leather industry but also secured several other patents for screw drills and other automated equipment. Sometime in 1902 , he established a second business for a bottle washing machine and your bottle capping machine. The company was located within the same building at 78 Sagamore street and the new venture was titled " The Gallagher Bottle Capping Company".The company stayed in business until around 1920's and was written about in the American Bottlers Trade Magazine. Bernard died a few years later in 1927, it appears as if the business closed prior to his death.
After seeing this capper up close, I suspected it was made around 1900-1910 , it's in exceptional shape and having the wrench and what apprears to be all the parts , you have a really nice piece of bottling history. My sugguestion would be to take several hi rez photo's of it and send it off to Sotheby's for an auction and insurance appraisal, they may have sold one like it over the years. It's also worthy to mention that it may have been used for soda waters, instead of beer, simply because of the manual nature of the machine( one bottle at a time, powered by foot). most breweries at that time where pretty fully automated by 1900, unless of course it was a very small regional brewery.