Silver Surfer wrote:
Noticed something peculiar while wrestling with the microwave this
evening. My assumption is that the digital display is a vacuum
fluorescent type.

With the board dismounted for close visual inspection I can see two
little metallic fingers connected to a one of the display's "pads" on
the right side. The fingers seem to be touching the inner surface of
the glass. There appears to be an identical arrangement on the left side
of the display; however, there is a circular blackened area on the
inside of the window where the left side fingers make contact.

Every VFD display I've seen has a dark area like that. I think it's
where a 'getter' was used to remove any remaining free oxygen inside the
sealed glass envelope. You see them a lot on other vacuum tubes, too.
Basically a metal that oxidizes easily is placed inside the tube before
it's sealed, then once everything is sealed up it's heated somehow until
it vaporizes. It combines with any remaining oxygen inside the tube and
leaves a deposit on the inside of the glass.