There is also other abbreviations on the card. On the left of ISS, you can see “DD”. If you wonder what is DD on California driver’s license? DD stands for “Document Discriminator” which shows your number and also these numbers indicates which you got your license from. What does RSTR stand for? RSTR stands for “Restrictions”. There are various restrictions which can be placed on a driver’s license. Most common example is, some drivers must have prescription glasses when driving.