Research Aid: Cryptonyms and Terms in Declassified CIA Files Nazi War Crimes and Japanese Imperial Government Records Disclosure Acts
The document states "REDTOP" is the CIA Soviet Division. https://www.archives.gov/files/iwg/declassified-records/rg-263-cia-records/second-release-lexicon.pdf
The CIA constructed a list of Soviet voice samples acquired during Mexico City operations.
This REDTOP document requested Headquarters information on Valentin Bakulin, the incoming Second Secretary at Soviet Embassy in Rio de Janeiro.