Stumpped on Bryant Furnace

Ran across an old Bryant furnace today and I can’t figure the age out. Model number was 39D4AC024080 SERIAL number was 39C81905. I was thinking 1981 but every thing I look up confuses me more can anyone tell me how to read these. Thank ahead of time.

It looks like the 39th week of 1974…

Bryant** (1980 - Present)**

Date of Manufacture (1980 to Present): The manufacturing date code is the first, second, third and fourth digits of the Bryant serial number and represents the week and year of manufacture.

For example: 40****86403525 indicate that this sample Bard unit was manufactured in the 40th week of 1986.

Year of manufacture: 4086403525

Week of manufacture: 40****86403525

Bryant** (1964 to 1979)**

Date of Manufacture (1964 to 1979): The manufacturing date code is the first, second and third digits of the Bryant serial number and represent the week and year of manufacture.

To determine year: R = 1964; S = 1965; T = 1966; U = 1967; V = 1968; W = 1969; X = 1970; Y = 1971; “Z” was not used; A = 1972; B = 1973; C = 1974; D = 1975; E = 1976; F = 1977; G = 1978; H = 1979

For example: 12****C123456 indicate that this sample Bryant unit was manufactured in the 12th week of 1974.

Year of manufacture: 12C123456

Month of manufacture: 12****C123456

edit: Larry beat me to it

Built 39th week of 1974 according to this info posted on here before:

From 1964 through 1979 Bryant encoded age information in the serial number with the first two digits indicating week of manufacture and the letter following those first two numbers indicating the year beginning R = 1964:

R = 1964
S = 1965
T = 1966
U = 1967
V = 1968
W = 1969
X = 1970
Y = 1971
A = 1972
B = 1973
C = 1974
D = 1975
E = 1976
F = 1977
G = 1978
H = 1979