This item presents a spectacular pair of imperforate stamp blocks from the 1921 first definitive issue of the RSFSR, featuring the symbolic "Science and Arts" motif—an allegorical composition that includes a book, a lyre, and scientific instruments surrounded by laurel branches. Issued on August 25, 1921, during the early Soviet period, this stamp embodies the ideological emphasis on intellectual development and cultural enlightenment. Each block consists of 5 × 5 stamps, printed using lithography on chalk-surfaced paper without watermark or grill, in a deep grey-violet tone. The stamps are completely imperforate, classified under Scott RU 183b, Michel RU 158za, Yvert et Tellier RU 146c, Stanley Gibbons RU 224, Unificato RU 146ba, and Zagorskiy RU-RSF 10BM. Designed by Estonian-German artist Günther Reindorff, this design was central to early Soviet philately. This set of twin panes—comprising 50 mint never-hinged (MNH) stamps in pristine, ungummed condition—offers exceptional symmetry and sharp printing for a high-denomination issue from a turbulent monetary era. Light fold marks are visible on the reverse, typical for large intact sheets of this vintage, but the face remains clean and vibrant. These blocks exemplify the transition from Imperial to Soviet visual language and are exceedingly rare in multiples of this size and format. Estimate "$300 – 400".