First of all, let me thank all of you who have pitched in on this topic. I certainly didn't expect it to range so far and wide.
I am in a position where I need to get rid of my collection in the next few years, so am currently trying to document what I have, so what I was really hoping for is whether I can list it as SG 52w or 53w. I bow to your more experienced opinions and will list it as "53w, or possibly 52w" since 52w has the lower CV: £9.50 vs £15.00. In any case, the stamp's condition is not all that good so it will not exactly create a major windfall one way or the other.
My holdings of WA stamps is pretty minimal, probably 20 to 30 in all. I don't have any other copies of the bistre/ochre stamp.
I would love to be dipping mt toes in your Western Australian tide right now. Shakespeare literally described the Canadian winter when he wrote "When icicles hang by the wall". (Photographed yesterday)
Re acquiring a copy of the Juhl study, I would love to but would be afraid that it could occupy too much time, given the amount of work I still have to do on the rest of my collection.
We have done a couple of rounds, seemingly coming from totally different directions but, deep down, I think that we have similar ideas on the problems of colour in Philately.
So, before we waste any more time on a relatively unimportant issue, I suggest we regard this topic as closed.
Again, thanks to all for your contributions.