1926, Esperanto Congress 7-14 rbl., liner perforated 11½, fresh color and good perforation, 7k. one negligible short perf at left, mint never hinged, very fine, these perforation varieties were printed in sheetlets of ten and are among the rarest of pre-WWII Soviet Union issues, certificates Dobin and Mandrovski (2000, 2005) (Standard 151-152A)
