4 ms·

It makes it more difficult to reseal in a non-noticeable way after someone has opened the the envelope and read it.

• IshKebab 8y ago
  Although in practice you could just put it in a new envelope... That actually seems like an advantage these letter "locks" have over envelopes - e.g. the butterfly one uses the middle of the letter to form the lock so it would be impossible to open it and then re-lock it.
  • deleted 8y ago
    [deleted]
  • varjag 8y ago
    Then you'd need to fake the handwriting on the new envelope too. Which is certainly could be done by Soviet security apparatus: they could even write the whole letter, or even make you write the letter they want really. But it's a lot more bureaucratically involved and requires totally different set of skills than what a minder at postal exchange has.
    • BrandoElFollito 8y ago
      And have appropriate stamps from all over the world. People collect these so it may not go unnoticed.