Tough question.
I regard it as "The Bible" for Postmark ID
However it only gives a rough estimate of scarcity, without values. (32 Pages)
What most of us do, in Oz, is to marry the ID, with sales at "Premier Auctions"
for values.
Then there is the Western Australian Study Groups 21 x *pdf's
on WA Postmarks A-Z
There is also Moguns Juhl Catalogue
also, John Dzelme 1976 catalogue
All should be desired to give a good in depth avenue into WA Pmk collecting
which is very popular, some WA dealers specialise in this discipline.
http://www.wastudygroup.com/postal-...illustrated/