Your truck looks like a 1950 to me...The 1950 trucks don't have vent windows, the 1951's do.
Check the body serial number to confirm the year. Fire departments are know for being slow in getting titles for their truck and it may have been first titled in 1951, but was built as a 1950 model.
Mike B

This truck has an odd serial number on it. It doesn't jive with any of the s/n conventions I can find. The number is:
3TJ-D 1170.
Now I do know the suffix on the big trucks didn't usually have the leading "00" like the lighter duty trucks had, but the prefix on this one is throwing me for a loop. It should be "UJ", not "TJ". It is definitely "3TJ" though. I didn't get a title with it and the license plate that's on it is from 1986. Not very likely that I can run it, although I haven't tried it yet.