The Dutch government makes carrying an identity card compulsory

From April 1941 onwards, every Dutch person aged 15 years or over had to have an identity card. This identity card had a passport photograph and a fingerprint of the bearer as well as a unique number. Large capital ‘J’s were later stamped onto the documents of Jews, to make them instantly recognisable. From 1 January 1942, everyone had to carry their card with them at all times.

For the Nazis and the Dutch police, identity cards were an important tool in tracking down Jews, resistance fighters, and people who wanted to avoid compulsory employment. The identity card had been developed by Dutch civil servant Jacob Lentz. He was also the one who set up the population register and the registration of Jews.

Because of the special ink, stamps, glue, and watermarked paper that were used, forging identity cards was almost impossible. Moreover, the identity card’s unique number could be used to check the data against the local or national public registers.

In this way, even ordinary police officers were able to detect almost perfect forgeries if they checked them thoroughly. The only way to forge identity cards was by feeding the data of non-existent people into the central administration. These data could then be used to create new identity cards. This required the cooperation of reliable civil servants.

Lentz's perfectionism cost many of his compatriots their lives and caused great problems for many others.