Those are commonly known as Craftsman 109 lathes, after the model number which starts with 109. A different lathe than the similar sized 6" lathes made by Atlas which had model numbers starting with 101.
These were made from the late 1930s until the 1950s, and there are a variety of different model numbers. Sold by Sears under the Dunlap brand and then later Craftsman. They also came in two lengths 12" between centers and 18" between centers. They are very light duty and simple lathes, but they have a fan base and are pretty common whole or being parted out on eBay, Craigslist, Facebook etc.
I can see they have the ridged headstock, so if they have Craftsman badges then they would be WW2 vintage. In the late 1940s they changed the headstock to a cast housing with a piece of engine turned aluminum or stainless steel for decoration.
There is probably pretty decent parts interchange over the years / models, but there are also some parts which are unique to certain years / models. The headstock is one area where there were fairly significant changes.
You can find more info on these here.
Dunlap / Craftsman 109
They are not made by Atlas, and have no relationship to the 6" Atlas lathes which were much better made. They can however use the change gears from a 6" Atlas.
