During the 1950s, european agents of any sort would have been carrying WWII (or before) firearms like the Luger or Walther P-38, Radoms, some of the Star or Astra pistols. You may even have found a few 1911s and even some snub-nosed revolvers there too. From the Communist perspective it would have been the TT33, or a broomhandled Mauser, for the heavier calibers.
If assasination was called for the would have used smaller calibers such as those found in the Walther PP/PPks, Berettas or Brownings and would have been used with silencers. There were reputed to be a few Tokarevs rebarrelled for the 32 acp and used with silencers but subsequent to that the Russians developed a sub-sonic round for the Tok - don't know how well it worked though.
The Communists had also developed a number of other secretive means to eliminate people, including wiping out entire willages, using poisons and specialty weapons that delivered fatal viruses or diseases. They were not usually so sophisticated about this that one might wonder how someone died as there was usually no doubt they had been assasinated.
The use of silencers was also problematic to the europeans for a while - the actions used on the Luger pistols did not usually support the use of a silencer - same with the P-38s - neither of those actions would function reliably with a silencer attached and at that time the Europeans did not use slow heavy bullets the way the Americans did with their 45s which are more easily silenced. The Tok is too fast to be silenced effectively.
Some folks have the picture of a 1950s - 60s european agents in white suits with Panama type hats hanging around north African or mediteranian ports and cities carrying a small pair of binoculars or a pocket camera, and a Browning, Beretta or Walther pistol in their pockets. Highly romanticized. HTH. Mikey.