This tartan actually has its origins in the Duke of Rothesay tartan, first seen in a kilt dating from the 1840s. The Duke of Rothesay hunting tartan was made by simply reversing the red and green -- we know this variation existed at least by the 1940s.

ITI notes on the Price of Wales tartan indicate that this was originally supposed to be the Duke of Rothesay hunting tartan, but a mistake was made in the white pivot, and the resulting new tartan was called "Prince of Wales."

Weaving errors are responsible for more "new" tartans than most people know!

Matt