It's interesting to note that, although it's highly redacted, Ivan Obyedkov's 47-page 201 file wasn't released by NARA until 2018.
Obyedkov was the Mexico City Soviet Embassy security guard who volunteered the made-radioactive-by-KGB name "Kostikov" to an Oswald impersonator over a sure-to-be-tapped-by-CIA phone line on Tuesday, October 2, 1963.
James Angleton talks about Obyedkov (on MFF page 16) of his June 19, 1975, Church Committee testimony, and as "another hangnail" in his February 11, 1976 Church Committee testimony, but in the former the stenographer (or court reporter, or person who transcribed the tape) misspelled his name as "Byetkov".
(Note: the documents are arranged chronologically, most-recent-to-oldest)
https://www.maryferrell.org/showDoc.html?docId=157254&search=201-779495#relPageId=1&tab=page-- MWT
