I was looking through digitized materials in the Australian National Archives when I came across this “mirror typed letter” that was sent to Captain J. L. Chapman, a member of Force 136, a branch of the British Special Operations Executive that fought behind enemy lines in Malaya during World War II.

As one can see, it is impossible to read, but when held up in front of a mirror, it looks like this:

Here’s what it says:

Dear Chappie,

I don’t know that this will reach you but here goes; Penghulu is worried stiff about those RODS you gave him. That Bastard Babu (or maybe Havildar) tipped off the boy scouts about the Ladies from Bristol. The scouts turned on the heat and demanded the roscoes. Pungie gives with the oil and weaves the following fantasy; Quote; The roscoes were under cover at the Yankee joint in prep. for a son of Paradise shindig. No Nips, no roscoes. Check your oil if they buttonhole you. Otherwise Pungie will be written off. I gave with the jive that the roscoes were a Christmas present from my watery cousins and would be dished out to Pungie only in case of the old nip one-two.

I have been rocking the home team with a lot of hot poop. Sorry I can’t beat my gums about it but will give you the office in Singapore. Needless to say, old cock. You pukka sahibs have had it. Regards to all the lads. Good luck.

P.S. I am sealing this epistle with wax. Please read and destroy.

I have no idea what this means, but I do see slang and humor. Slang and humor are difficult for outsiders to understand, but I never imagined that they could be used as a secret code during wartime, but obviously they can.