Steve,
The last official DWM year was 1929. As they shipped the machinery to Mauser in that year and Mauser needed some time to setup and start producing themselves there can be legit DWM toggles dating from say 1929 - 1934. Experts can give you some more insight.
This particilar pistol simply had it's receiver swapped out for another one.
I am the proud owner of a 1936 DWM

(which of course also got a fresh receiver somewhere along the way)