Typical of the simple lathes intended to re-machine the armatures of electric motors and dynamos, the 3-inch centre height by 12 inches between centres Parker McKnight was built in Cincinnati, Ohio. As with other makers, the McKnight employed a pair of Jacobs chucks, one in the headstock and one in the tailstock, to hold each end of the amateur shaft. In order to allow the part to rotate, the tailstock chuck incorporating a bearing that allowed it to act as a rotating centre. No doubt a variety of specifications was offered - though the example below lacks its own motor-driven mica under-cutter head - as shown here on the Atlas-made version
Other specialised armature lathes have include the Frankwood,  Sherman Clark, Burton & Rogers and  adaptations of the Atlas 6-inch and Weidenhoff/.
Should any reader have a Parker Knight lathe, or any literature about them, the writer would be interested to hear from you..