A quick search showed me that a lot of 15 of them had sold in a Heritage auction last year. The lot went for $33. And they appear to be British in origin. No mention of their function or reason for being created. I suspect testing some printing equipment.
They are used to test ATM machines https://en.numista.com/catalogue/exonumia304847.html De La Rue plc is a British company headquartered in Basingstoke, England, that designs and produces banknotes, secure polymer substrate and banknote security features (including security holograms, security threads and security printed products) for central banks and currency issuing authorities. It is listed on the London Stock Exchange
That's EXACTLY what they are for, testing ATMs. I used to repair ATM equipment for Diebold. De La Rue has also printed postage stamps for many decades. I'm not sure if they still do.
