Quote:
UN section was the 2022. Starting with 2023 ... split out into individual book
UN became stand alone in the 2023 series as did essays and proofs which received much updating. 2022 saw the removal of the regular issue identifier to a stand alone.
My guess is the no longer stamp issuing territories may be split off eventually as well, CZ, Cuba, Guam, etc. into a stand alone volume. If Scott got really desperate anything starting with an "R" with or without following letter or letters would be moved to a revenue volume. That would upset the RW (Duck) collectors as that series continues while all other federal revenue flavors and series are dead.
Me, I have my 2021 for the identifier. I will buy a essay and proof catalog eventually but my 2022 works fine.
As to UN my 2021 or 2022 work fine as there is nothing of interest issued since the 1960s and in this century nothing issued but wall paper which is 99 or 99.8% blocked from ever being used on real mail ever again. They, the UN, are quite happy to sell the stamps, not so much providing actual mail service.