The old folding handkerchief trick

Noticed this on Twitter not so long ago, with the handkerchiefs on display in some police museum or other in Malaysia:

 

I can tell you, Googling the topic "folding porn handkerchiefs" or "vintage porn on handkerchiefs Malaysia" has really thrown up a lot of results I didn't want, and nothing useful!

This reminded me of the old Mad Magazine fold in cartoons.   Wikipedia tells me they started in 1964, and were done by the same cartoonist - Al Jaffee - til 2020!  (Jaffee is now 101!  Talk about a long career.)

Anyway, I'm not sure that it took much imagination, looking at the drawings on those handkerchiefs, to see how the right fold could make it look like sex.   But I wonder how common this means of distribution was - just a South East Asia thing, or were they all over the West too?   Can't say I have heard of them before...