According to my foolproof chart (which usually proves to be a fool)…
ANNNNNN This serial number was used from 1969 to 1990. The first alpha character is for the month of production. A-M = Jan-Dec 1969-1979 N-Z = Jan-Dec 1980-1990
So the letter “R” would be May…
(‘I’ and ‘O’ are not used)
The second digit, a numeric character is the production year
The balance of the numeric characters are the production sequence
e.g., A912345…this serial number would be a unit produced in Jan 1969
P512345…this unit would have been produced in Feb 1985
Neat chart David. The CARRIER HVAC section agreed with my chart. I wasn’t all that sure about mine because it’s quite old, but I feel better about it now.
And I’m going to file your chart for furture reference. Thanks…