Quote:
Are there any online resources about the relative scarcity of Hong Kong cancellations?
Opinion.
This is where general philately, jumps to another level.
I find I have to employ
Google searches
Dedicated Blogs that match your query
Searching for dedicated catalogues, dealers.
Joining dedicated societies with hopefully, printed journals.
SCF Linus, here has written interesting threads on Treaty Ports.
he may weigh in with further routes.