Serial F1874 4593. If it’s 1974 I’d be quite surprised because the unit is in very good condition.
do you have the model #??
Comfort Aire is a tricky one with a gazillion bazillion different types of coding. I don’t think that one is 1974 because then I would be expecting F7418.
My inclination is that there are at least two digits missing in front of the F. If that’s not the case, though, then I believe your F represents June, and your following numeral 1 is for 1981, 1991, or 2001.
Put that information with the construction date or, if a very old house, look at the recent mortgage history. Many people take out some home equity to install major appliances, so if your mortgage history shows a $15,000 loan in 2001, I’d go with 2001 as the manufacture date.