From April 1, 1892 till April 1, 1957 there has been a reduced rate for local shipments (with an exception in 1921-1928. This letter (19.10.1953) was sent from The Hague to the neighboring village of Wassenaar, but local was local, so the full letter rate was applicable. The sender thought however that it was so close by that local postage was sufficient.
So the sender glued a stamp of 7c on the letter, the local rate from July 1, 1953 till the end of the local rate, April 1, 1957. The post office didn’t agree for the rate had to be 10c. According to the rules, the missing 3c leads to a postage due of 6c.