I can't remember for sure, but some of the much older lathes may only had one half of a half nut. As for the thread dial, the older lathes were not equipped with a threading dial. This is something that started showing up on lathes in the late teens early 1920's.
Please post some pictures. That would very much help us out here trying to help you out. On another note, I believe Monarch Lathe wound up buying out Sidney Lathe.