Great Unit for Postal Rates Specialist. 1921-23, 22 covers, representing franking by various Imperial stamps (issued in 1917-19) and practically all RSFSR issues, all are internal mailings, many to/from Moscow and Petrograd, some registered items, approximately a half sent in 1923, when rates changed like in a kaleidoscope, in addition one early cover from Imperial Russia and one from Russian Army in Latvia, minor conveyance flaws, still F/VF, Est. $500-$600 (Image)