[rotorwrench]

A 1941 truck could have been 19T prefix unless they continued 99T from 1939. The CCC or Civilian Conservation Corps may have purchased the vehicles on a contract basis which could have carried through from the year of the contract like the wartime trucks did. Most trucks for wartime were ordered on a 1942 contract until close to the end of 1944 and early 1945 when they had to start new contracts.

Also, Mercury continued the 99A prefix even after the war so it may be more likely the trucks bigger than 1/2 ton did as well.