John "Jack" O'Sullivan was an umpire for semi-pro Doherty Silk Sox games in New Jersey in the early 1920s. Multiple newspaper clippings mention this connection, including a
write-up from The Record announcing his promotion to the National League in late September 1922. I was finally able to find
this great article in Newsday detailing his career as a boxing referee and baseball umpire, including the Silk Sox and the National League, though they were off on his tenure there by a few years.