Hi,
It may not be a PP weight. According to John Simmonds, Perthshire did a number of limited editions for specific shops/outlets (in his book, he shows a limited edition teddy bear weight made for Harrods). This could be one such edition. Often these 'rogue' editions are not recorded anywhere.
Personally, I cannot remember seeing your weight before, but others on this board may have. It is very pretty anyway.
SophieB