Noces Rituelles was broadcast in D2MAC on TV Erotica many years ago. The channel also carried Teletext which was recordable due to it being in D2MAC, so when I recorded the film I usually also recorded the teletext information as it had castlists and brief film information.
At the time I also knew the channel's programmer as I did regular work for him for another of his ventures.
It is my understanding that the teletext information came from the boxcovers/sleevenotes.
On the teletext Sylvia has a surname - Sylvia Duval.
So on the basis of the existing presumptions XNK1521 = Sylvia Duval.