Greetings from Downunder!
Well, my mistake! They are not Royal Yacht glasses but "Masius". My research tells me these were a glass with the seal of Holmegaard's then advertising agency "Darcy Masius MacManus back in 1980. Some of this information I found on the Hardernet web site and the rest fell into place with a little "googling". End of problem, we can all rest now!
Barry