Of traditional American WW (Webster Whitcombe) design, the 50 mm centre height, 8 mm collet Zimmerman was stamped on the end of its bed: M.R. Zimmerman Mach. Wks. Holsopple, PA. U.S.A.
In the 100 years spanning from the middle of the 19th to the middle of the 20th centuries a very large number of watchmaker's lathes were produced, with many re-branded so as to appear by other than their real maker. Hence, although Zimmerman might have been the maker (and the stamping Machine Works would lend credence to this) there is no surviving evidence as to their manufacturing capabilities - nor indeed to any other horological tools they might have produced. Hence, it is just as likely that they were a supply company who commissioned a batch of lathes from one of the better-known makers. On each example discovered so far a number has been stamped into the end face of the bed; rather indicating a model type these would seem to be Serial numbers, the highest so being "39"
Appearing to be a rather "beefed-up" lathe in comparison to the 8 mm Peerless/Marshal types with a more massive bed and fitments (a comparison photograph is shown below) perhaps the intention was to offer a watchmakers' lathe capable of heavier-than-usual work while preserving the fine feel inherent necessary in such a small machine.
If the finish is chrome - and it appears to be - the seldom-encounterede Zimmerman would have been made post 1930 - a point at which the finish started to become widely available. See also: http://www.lathes.co.uk/watchmaker