The BBC rounds up revelations of the nefarious typewriter;
...paper and typewriters still have vulnerabilities - and the Russians should know this. For instance, it's possible to reconstruct from a typewriter ribbon some of what was written using it. This was done with a ribbon found by the FBI amid the rubbish of CIA officer Aldrich Ames, who had become a double agent for the KGB, and the resulting text revealed plans for a meeting in Venezuela.
There are even more ingenious ways to spy on a typewriter. In 1985, CBS News reported that Soviet agents had installed sensors in a dozen typewriters in the US Embassy in Moscow. "The devices picked up the contents of documents typed by embassy secretaries and transmitted them by antennas hidden in the embassy walls," CBS said. The typewriters used a round ball with numbers and letters around the surface, which revolved before hitting the ribbon against the paper. The bugs could work out each letter typed by detecting how the ball moved.
A National Security Agency study of the episode, largely declassified, notes with grudging admiration that the bugs - 16 in total - had been put in place by customs officers when the typewriters were shipped into the country. They had gone undetected for about eight years.No mention of the speed with which the secrets were typed.