I had seen this item and the urge to click was sore upon me, but I said Get thee behind me, curio!  Now you tempt me again. I must be strong.

I believe these predate personal slide projectors and were for use in public venues for messages like "The management request that you refrain from cigar smoking during the performance". Name and the spark image have a 1920's feel. How wonderful it must have seemed to be able to talk over invisible electromagnetic waves over the air! Could they have been used to project messages to the studio audience during radio broadcasts?

Those are very interesting! It would be easy enough to replicate the effect I would think using the right materials and I suppose you could become very creative with it. I wonder who the target collector for these things might be? Photographers? Those into film? Certainly typewriter enthusiasts, Repartee aside, must be low on that list.