Normally the Model 21 Standard Grade was not marked. In the early years the Model 21 was offered in the Standard, Tournament, Trap and Custom Built Grades. When the Model 21 Skeet Gun was introduced it was offered in Tournament, Trap and Custom Built Grades. Similarly the Vent Ribbed 12-gauge Trap Gun was offered in Tournament, Trap and Custom Built Grades. By the 1936 catalog the Tournament Grade was dropped and the Model 21 Skeet Gun was offered in Standard, Trap and Custom Built Grades and the 12-gauge vent ribbed Trap Gun was offered in Trap and Custom Built Grades. Between the 1938 and 1939 Winchester catalogs the Model 21 Trap Grade was dropped and the Model 21 Trap Gun was introduced. Also the vent rib was now an option in all gauges and barrel lengths. In the 1941 Winchester catalog the 12-gauge 3-inch Model 21 Duck Gun was added to the offerings. Chambering any gauge for 3-inch shells had been an option from the get go. During the War years plain extractors and double triggers disappeared. The October 1946 catalog did still offer the Model 21 Standard Grade or Field Gun with a slim forearm and the Model 21 Custom Built Grade had become the Model 21 DeLuxe Grade. By the 1950 Winchester catalogs all Model 21s were single selective trigger, ejector, beavertail forearm guns and the entry level was the Model 21 Field Gun. By the 1952 Winchester catalog the Model 21 DeLuxe Grade reverted to being the Model 21 Custom Built Grade. The last change in the production years offerings was in the January 2, 1954, Winchester catalog when the Model 21 Duck Gun changed to the Model 21 Magnum Gun with the addition of the 20-gauge 30-inch barrel 3-inch chambered gun.