Ключевые слова: aged, antique, approval, canceled, cancelled, classic, collection, collector, communication, connection, correspondence, doctor, history, hobby, image, letter, mail, mark, medicine, neurophysiology, perforation, philately, physician, physiologist, picture, portrait, post, postage, postal, postmark, price, print, reflex, repin, republic, retro, scientist, sechenov, soviet, stamp, union, unique, used, ussr, vintage, zigzag,