Interestingly, the CCCC's popularity even caught the attention of the Central Intellegence Agency, as expressed in this passage of a recently released secret document on Soviet postal spying:
Letters containing orders or requests for stamps by catalogue numbers may lend themselves to clandestine transmittal of coded Information. It should be noted that these letters are not in violation of Soviet postal regulations. The RIS [Russian Intelligence Service] has used international stamp collectors' letters for agent communication outside the USSR to the USSR. "Cover" exchanges to and from the Soviet Union are not as prevalent as in other countries but there have been exchanges with the Western world. Probably the most widely circulated cover club in the USSR is the Cover Collectors Circuit Club with headquarters in Waterloo, Iowa.But then, one famous person (?) is alleged to have said:
["Soviet Postal Intelligence," CIA, May, 1962]
"You can't be paranoid enough"