I checked my production data book, but one crucial page is missing, so I cannot definitively answer your question. K15 production stared in November 1937 and ran through June 1941. I have K15 production for all years except 1939:
1939: 5128 total K production, all models
Given the above, it's highly likely that your truck was built sometime in 1939. Be aware that Stude didn't put much emphasis on the model year of its trucks. For example, K truck production started while J trucks were still being built, and continued to be built well after the introduction of the M series trucks.
Frank Drumheller could certainly answer your question, but he's still recovering from surgery and may not be on line for a while. And buying a copy of the production order from the museum would nail down the exact day your truck was built.
Posted on May 2, 2012, 4:48 PM from IP address 126.96.36.199