Lets be careful, here are the armature facts. XA5969 is the number of the first postwar steamer armature. It was used from 1946 through 9/49. beginning in 10/49 an oil slinger was added to the armatures and the number XA11077 was introduced, but many XA5969 armatures were made after 10/49 with oil slingers. The oil slinger armatures are 1/16" longer and require a different brush bracket to work. the laquer wire insulation changed from clear to purple in 1951. The color means nothing other than it looks different. All purple armatures have oil slingers.
Beginning in 4/51 Pul-Mor armatures were introduced, unfortunately with the same XA11077 number. These are easy to identify because they have very narrow pole gaps. These Pul-Mor armatures will work in a non Pul-Mor Atlantic or 290. They are completely different than the super armatures referred to as the "big motor."