Very strange mandolin pickup

This pickup of mandolin is very strange. Had never seen it before.
Attachment 155107
Also used on guitars
Attachment 155108

I suspected it was a Volu-Tone... and then I saw the Volu-Tone amp in the second pic! Check out this monstrosity on a lap steel:

Attachment 155136

They were sold as part of steels & guitars, and also on their own (sort of like a proto-DeArmond). The major drawback of these pickups was that their electromagnets had to be charged from the amplifier before use, and as I recall there were major electrical safety problems with the setup. I guess permanent mangets were still expensive enough in those days to make this a viable product, though not that many have survived.

Great sleuthing, nmiller! I had guessed an early steel guitar pickup.... but came up empty on a maker or model. Glad you solved the mystery. I enjoy learning about early amplification gear.