While I was working at the USPS one of my jobs was to operate a Letter Cancelling Machine. Once you feed the letters into the Letter Cancelling Machines the letter goes through about 40-50 U-Turns before coming out the other end. Any item that was not flexible would jam the machine and tear the envelope and drop into the bottom of the machine. After running all the letter mail that needed to be cancelled we would have to then clean the machine. I have found Coins, Chips, Tokens and many other items that what you called the monster tried to eat. One night when I was cleaning my machine I found 12 One Hundread Dollar Bills. I don't know what kind of person would send $1200.00 cash in an letter size envelope but I guess he deserved to loose they money. Yes the money was turned over to the U.S. postal Inspectors where it went after that I have no clue. Come on people buy padded envelopes for a little peace of mind. Just today I received 4 chips in a letter size envelope and the envelope was'nt even sealed but the chips were there. If you are going to keep using letter envelopes ask the clerk to hand stamp the envelope or you can write non-machinable . I am not sure how much more it will cost but at lease it won't go through the BIG POSTAL MONSTER