Reference 4134 was produced in limited numbers from 1942 to 1947 and is one of the very few self-winding Rolex watches with snap-on back. The caliber 620 was created in 1936 and was in regular production between 1940 and 1951. This watch is illustrated in ?Rolex Collecting Wristwatches? by Osvaldo Patrizzi 2001 Edition p 61.