USSR 15 Kopeks 1928

C.C.C.P. - Union of Soviet Socialist Republics - regular issue. This design lasted from 1924 to 1931, the last year is rare.
VIEW & DOWNLOAD:
The Coinage of Russia, 1921-1935 by RW Julian, a great article at this: https://groups.io/g/Moneta/files/Moneta%20Library/Russian%20Coinage%201921-1935_Julian.pdf
For a great review of Russian coins from Rus through the Revolution see the Library at:
Russian Coins - 1000 Years: https://groups.io/g/Moneta/files/Moneta%20Library/Russian%20Coins.pdf