It is fair to say there has been an evolution of the design, as far as I can tell (judging by the shapes it is found on) the spiralling brown and cream version may be the earliest variation with the more random or artistic trails and the grid like patterns following.
The Dexham catalogue is not a comprehensive sample of the factories output at the time.
When Harris left Malta he wanted to leave the studio in a viable position despite the fact he was forced out by the Maltese goverment, he effectively gifted them Ming, Crystal Blue Stripe, Tortoiseshell, Earthtones, etc. His old friend Dobson was still heavily involved there and the decision was made to differentiate the new output - hence the general change to more angular shapes and more flared rims.
Harris did not leave a single piece of glass behind (presumably it was all sold one way or another) nor did he leave any materials behind, they were the materials he started production with at Isle of Wight Studio Glass, think of those blue green pedestal paperweights - in typical Mdina colours.