AC age - Intertherm unit

Where could i find a serial info for determining the age of a Intertherm AC unit?

3rd and 4th #'s of the serial number, I believe, is the year. Do you have the #??

The info I have is the 4th and 5th digits are the year, and 6th and 7th are the month.

1219 87my20 01 - ser#