Please. 
M# 40AS024320GM
S# C7A07713
TIA
Age: Through the 1960s Carrier used the first digit of the serial number to indicate the year of manufacture. Example: 3xxxxx = 1963, 4xxxxx = 1964, 5xxxxx = 1965, etc.
Beginning in 1970 Carrier began to use a letter followed by a single digit year.
Example: A1 = January 1971, B2 = February 1972,
M5 = December 1975
Note: No letter I
A=Jan
B=Feb
C=Mar
D=Apr
E=May
F= Jun
G= Jul
H=Aug
J=Sept
K=Oct
L=Nov
M=Dec
More recently Carrier has simplified things using the first four digits of the serial number to signify the age, where the first two digits indicate the week and the third and fourth digits indicate the year of manufacture (similar to Bryant).
Example: 3298xxxxxx = 32nd week of 1998
I had this in a file also.
Carrier, Bryant, Payne, Day & Night: Recently (last 20 years or so) the first four numbers in the serial number represent the week and year. Previously, it was a complex series of letters and single digits. Call 905 672-0860 if you get stuck.
I had the lower part (and they’re closed now)
Thanks for the upper part - now on file. 
1977 seems right for this place.