1927 Sc O215 Black 8K surcharge on 1925 7K “Decembrist” Scott 354

1927. Black 8K surcharge on 1925 7K “Decembrist”. This stamp had never been in normal postal circulation, but was sold at philatelic stores, also exist with CTO cancellations.
Catalogs: Scott 354, Standard Collection O215, Michel 337A.
Issued on: December, 1927.
Perforation: 12.5.
Printing: Photogravure.
Surcharge: Typo.
Face value: 8 Russian kopek.