The key part is when the anonymous buyer remains anonymous. If his invention works, why not patent it and let everyone see the internals?

EDIT: Looks like there supposedly is a patent: "a method and apparatus for carrying out nickel and hydrogen exothermal reactions," with production of copper, though I haven't found the patent itself.

http://www.nyteknik.se/incoming/article3080659.ece/BINARY/Ro...

Seems like someone would independently make one though.