I have been collecting worldwide used singles since the 1970's and, over the years, have set aside several diffeent types of items which I don't collect.
Perfins ... The Perfins Club ( https://www.perfins.org/
) holds auctions for members, but provides free one-year memberships.
It seems to be very well run (nice periodic hardcopy/internet bulletin, a classification system, samples for new members, easy communications, etc.). My experience, and the $$, was great! I started by writing to the Auction Manager ...*** Moved by Staff to a more appropriate forum. ***