"When it was brand new, i've measured the frequency at ~35KHz, modulated by
100Hz (double rectification of the mains' frequency). "

So they don't bother filtering, like a microwave. Hmmm.

"I've been using Corning glassware and Corningware for years, and have never
had a piece break while cooking. Dropping them is a different matter. "

Visions were different. Some sort of superglass. The commercial showed them melting a conventional metal pan in their glass pan. I would imagine it was not stainless, IIRC the melting point is quite high compared to aluminum or steel, or cast iron.

But these things didn't just break, they exploded. They are no longer on the market, at least with the old formula.

It is pretty cool to be able to see what you're cooking like that. There was always Pyrex as well. One of the things visions touted was an extremely high thermal mass. In most cases if you wanted to cook say spaghetti, once it came to a boil again with the pasta in the water, you supposedly could shut the heat off and it would cook fully.