Provari’s I do not know.
From an engineering standpoint, it might be something that would interest you Mooch. Not sure if you've heard of ProVape company or the ProVari before. The company was an early pioneer of American-made, variable voltage devices.
The company was founded by former employees of the Washington state aerospace industry. They put in a lot of effort to make quality devices with military-grade wiring. Sadly, the company closed shop in 2017 due to the uncertainty of FDA regulations. So you can only get them used now. There's still quite a loyal following of ProVari users.
Anyway, to me it is an interesting piece of history.
ProVape Says Goodbye to the Vape Industry - Vaping360