Date code For Armstrong Furnace

Does anyone have a Date code chart for Armstrong Furnaces? I have one for the Armstrong A/C but not for the furnaces.
Model: [FONT=‘Times New Roman’]GUJ125D20[/FONT]
[FONT=Arial]Serial: [FONT=‘Times New Roman’]8499F63244[/FONT][/FONT]
[FONT=‘Times New Roman’]****[/FONT]
[FONT=‘Times New Roman’]** Thanks, Ken**[/FONT]