Age of RHEEM furnace

Specific Inspection Topics Inspecting HVAC Systems
1

Model # is RGDA-100C-ER, Serial # is CN 3D104 M3688 5406. Please help

2

I’m looking for an “F” in the serial number…don’t see it where the “M” is but it is probably an '88.

3

Ditto Larry, Looks like the 36th week of 1988

4

Yep.