I didn't think about regional differences. I forgot how important that is.
I'm inclined to think about the southwest, from the bay area to Arizona and local points to San Diego.

In that area, road crews had different slang terms and the work was similar but different enough. Swing Brakeman referred to that which would work retainers, handbrakes, short work near the middle part of a train. A Foreman is a yard 'conductor', with similar but different work rules.

Mostly, I'd like to know if the Tagman was the Foreman or did he do the top end work with the Foreman while the Field man did his thing?