UB5BO 1958 Ukraine

Concerning call signs in Cyrillic:
During the period 1951-1956 – HAM in USSR were forbidden to conduct QSO with correspondents from capitalist countries.
Therefore, it was forbidden to indicate the callsigns of Latin letters to QSL.

QSL from the estate of W3DAZ / K2GHM / N5KH
Info courtesy of UY5XE