Hello, 930,
That one appears, from the photo, to be a mid to late 1920's machine, alright, Its serial number will be in the 2000's range, I should think.
It appears to be one of the 'first iteration' of the Monarch 'helical gear headstock', with Timkens on the spindle, and threaded spindle nose. It will be an 8-speed machine, with a top speed of 4-hundred-something, the normalcy before carbide tool-bits, when only high speed tooling was available.
That model is not as desirable as a mid-1930's Monarch would be, with the later 16-speed headstock and camlock spindle, but if its in reasonably good condition, it will do pretty much anything a later model lathe will do, just not as quickly.
What is important is 'condition, condition, and condition'. Check for bed, cross-slide, and screw wear. If its unworn, it will do good work. If its 'somewhat worn', it may be cost-effective on open tolerance parts, or for the roughing-out of parts which will be brought to finish dimensions on a lighter belt drive lathe. You'd be surprised at the amount of cut that Monarch will take, in alloy steels and the stainlesses.
cheers
Carla