I have a Payne package unit that I am trying to see how old it is.
The M#: 30-80YAC-106C
The S#: FDMCB25692

Can some one please help?

guessing,, not sure about payne,, June of 1992,, 692,, and 2.f ton air=30-

There is no date of manufacture listed on the name plate?

Probably right,, like I said ,it was a guess