Outstanding pair of imperforate blocks of 4, denominations 3 Lei and 6 Lei, from the 1931 “Taxa de Plata” (Postage Due) issue. Printed in black on white paper, both mint never hinged (MNH), with full original gum and fresh impression. These imperforate proofs were produced in only 200 copies each, intended as presentation sheets for King Carol II and not for postal circulation. Such multiples are almost never seen on the market — most known examples are single stamps or pairs. Both blocks are imperforate, pristine condition, full gum. The 3 Lei block shows top sheet margin. Superb centering and clean design with the royal crown motif. Condition: MNH, perfect gum, no faults. A great rarity of Romanian philately, representing one of the most exclusive back-of-the-book issues of the interwar period.