Where does this light go?

Having more adventures under the dash of my ‘68 300. I came across this light dangling behind the convenience tray (ash tray).

It is a very small bulb completely encased in metal with a small window to let some light out under that (brittle) blue cap.
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Looking at the FSM, I am almost positive it is one of these “Ash Receiver Lamps”, I just can’t figure out where it attaches. And I can’t find the other one either…...

Where does this light go?
Author: SPF Required