Is this a recreation or adaptation of an existing lathe add-on mechanism or is it a wholly new device?

It seems (to me, at least) pretty well designed to retain perfect concentricity of the shaft or part you're adding the polygonal feature to; reducing the setup time and possible error required to move it to the mill to machine the flats, and quicker than setting up a separate spindle on the toolpost to mill them woth some sort of dividing fixture on the headstock.