These are miniature indicator lamps that I found in the collection of parts at Corvallis High School.  I don't know any rating or lamp type information.  They have no bases, just wire leads extending from the glass envelope.

I took all the lamps (maybe 100?) and put them into a Pyrex coffee urn that has all non-glass items removed.  The lamps were covered with about 25mm (1") of water.  The water gives the microwave oven a 'load' (a place for the energy to go) and it keeps the lamps from getting too hot.

The microwave was turned on for about 20 seconds at a time.  Like the other experiments where the lamps are completely submerged, this experiment can probably continue as long as the water doesn't boil too rapidly.

 

Lamps under water in the Pyrex coffee pot.
The turntable was allowed to rotate.
As with other experiments, light intensity varied with the location of the coffee pot.