Patient ID numbers in the UK's National Health Service
When I lived in England my medical cards always bore my patient ID of 5 letters, 3 numbers. That numbering system is now obsolete.
mst3kmoxie and I, previously having used the NHS in England, have our Scottish medical cards bearing both a 10 digit NHS number and a 6-4 digit CHI number; our children's show both a 3-2-4 NHS number and a 6-4 CHI number. I am surprised by the 3-2-4 format of my children's: I wonder if it is just an oddly spaced NHS number without its check digit.