WARNING: This image is highly speculative. The main source pointing to this design is the Catalan Atlas, which as a historical primary source cannot be considered a reliable reference, especially if it is the only source used. This image should not be added to articles without clearly indicating its speculative nature.  Note that FOTW (where most of those flags on Commons are adapted from) is based on user contributions like Wikipedia, and hence not authoritative either.
Own work
SanchoPanzaXXI