While attributing the mount to Mogey is reasonable I'll point out that there were a number of other New York-area telescope makers that used very close variants of that mount design such as John Byrne, Wm. T. Gregg, Wm. Gardam & Son, Henry Fitz, Gundlach, James W. Queen, Gall and Lembke and perhaps others I'm forgetting. I believe it's possible they were supplied by the same specialized machine work company initially, as a subcontractor to the various makers, but the large number of Mogey mounts seen later, well into the 20th century, suggest the patterns and designs wound up under their control in New Jersey. Here's some quick photos of similar mounts that came with different makers' telescopes:
In order they're from Mogey (note the similar hex to your new mount at the base of the polar axis casting), Gall and Lembke (the telescope tailpiece is signed by them, but the objective is signed by Byrne), Queen and Co, and finally the brass Henry Fitz equatorial. I believe that the Fitz mount may have been made by Jonas Phelps in the 1850's. It's the earliest of all of these, and he might well have been the original designer of this family of mounts, with others modifying the design over the next 70 years or more.
All that said, it's at least possible that one of these guys (and gals in the case of Fitz, who employed women) made the entire thing.