Wizard of OZ?
This element came out of a Turner BX. Judging from the patent notice on the back, this element was built sometime after 1931, so I'm putting it at '39, but I'm not certain. This element works! But I wouldn't use it for harp! When I tested it out, it sounded great for the first two minutes. Then it started to fade out over the next 30 seconds till it was nearly silent. So I put it on the shelf for a day and tried again. Once again sounded great, but died again after a minute or two.
I figure the crystal inside is so old, that when I'm playing harp through it the crystal gets saturated with moisture from cupping the mic and playing. When it dries out, it sounds fine again. So I'd look at this only as a vocal mic, and then the quality sounds just like 1940's recorded radio programs.