I've read that wax seals were meant to guarantee the authenticity of letters in ancient times. How hard was it to forge wax seals, and how often did this happen?
Hi, there's room for more input - especially wrt "ancient times" - but fyi a similar question came up recently which was quite popular
and also
While a counterfeiter could copy the details if a stamp used for wax seals, such as numbers, letters, and images, one thing he could not copy was the imperfections. A stamp would have bumps, chips, and other imperfections that could be identified as the legitimate seal, which were too small to be copied artificially. One who is accustomed to seeing these seals would be able to point them out when examining the seal.