The fact of the matter is that the DD-214 did not come into existence until the American military forces were consolidated in 1947 into the Department of Defense (see-DD!) The Korean War was the first U.S. military conflict to feature DD-214's. There were no WW1 or WW2 DD-214's!
Before January 1, 1950, several similar forms were used by the military services, including the WD AGO 53, WD AGO 55, WD AGO 53-55 (For Army and Army Air Forces personnel); NAVPERS 553, NAVMC 78PD, and the NAVCG 553 (For Navy, Marine, and Coast Guard personnel).
These separation/discharge certificates contain lots of good genealogical information, so, if you are doing military research, you should look for them. Just know what you are looking for. (Whew, glad to get that off my chest!)