John Sobieski Stuart and Charles Edward Stuart were names used by John Carter Allen and Charles Manning Allen, two 19th-century English brothers who are best known for authoring and promoting a dubious book on Scottish tartans and clan dress; the 1842 'Vestiarium Scoticum'. The "VS" purported to include clan tartans from antiquity. It is generally recognized that most were invented "whole cloth" by the brothers.
Most "1842 variant" tartans are designs which first appeared in the VS. This has not prevented them from being worn and enjoyed for years. Many, in fact, have become regarded as semi-official or official clan tartans.
Regardless of source or age, the final word on any tartan's status rests with the clan chief.