Needing this General Electric Furnance decoded

Hello, does anyone know if InterNachi provides us members a discounted rate for technical reference guides? I don’t currently have one, but at this point I am needing to-decode this manufacturing tag for reporting purposes. The year is needed with the input BTUs, sometimes I was told the ANSI # can assist, but was not successful at locating this either on the tag provided below.
The unit is a gas fired General Electric Furnace. Home was built in 1979.

Model # is Model BLU123C948B0
Serial # 502136

I would appreciate any assistance fellow team members!
Thanks John

GE manufactured that unit from 1974-1977. The BTU’s is located in the center of your picture of the data tag- 123,000 BTU’s.