3 r. on 7 k. together with Coat of Arms 7 r. imperforate, tied by cds. “IRKUTSK 21 12 20” to reverse of registered envelope to Riga with arrival cds. alongside, interesting franking paying the 10 roubles registration Soviet rate during the free post period (as Irkutsk was in Red Army territory), some imperfections and an horizontal crease, but a most unusual cover, signed Dr. Mertens