This is a full set of the Soviet souvenir sheets commemorating the 100 years of Russian postage stamp, cancelled in Клайпеда / Klaipėda, Lithuania SSR. Both souvenir sheets still have gum on the back which tell us that all the postmarks on them are actually CTOs most probably privately ordered since there wasn't any commercial mass production of CTO in Klaipėda as far as I know.
