There should be a sailmaker's patch at the tack of the sail (forward, lower corner). If it says "Hobie Sails," then the sails are legal for racing.

From about the mid-70's through the early 90's, the Hobie Sails patch was a white parallelogram about 7 cm long and 2 cm high. After that, it became a circular patch about 8 cm in diameter.