Help age Armstrong HVAC

Can anyone help with age of unit?

Thank you,
Don Maddox

Armstrong Concept 1200
Model # SCU12E36A-1A
Ser. # 8499J48150

I’d say sept. '99.

Lennox & Armstrong[FONT=Times New Roman,Times New Roman][size=3]: Either the first two or second two digits are the year, it varies by era, but most of them actually have a separate sticker somewhere that has the year printed on it. Newer units are first two equals manufacturing plant #, 2nd two are year and letter in fifth slot is month (A thru M minus I). So 5898G 07568 would be Plant # 58, Year of MFR would be 98 and month would be July. G9D-82-M were made from 1964 to 1968