Yes, stop, wait a minute 'Mr Postman' - as you are clearly an imposter! His disguise is almost perfect... but look at those correspondent shoes!! Obviously he could not find any proper postman's shoes to fit his ridiculously tiny feet. I'm not too sure about the cap, either, on his ridiculously large head. And a yellow tie? I think not.
The yellow pillar box is another mystery - perhaps he has an accomplice hiding in the fake postbox. As foreign spies in the 1960s, they had only ever seen black and white photos of Britain, and mistakenly supposed the postboxes to be yellow, as they are - in Lithuania!
Fortunately, the children are merely baffled by the messages of communist propaganda he is handing out. Some of them are too young to read, and the others are disappointed because they thought he was Tufty the road safety squirrel.
I think this child's hanky was made in the 1960s, and was possibly made as a warning to children to beware of spies in the street. Or not.