Current status according to W4190 chap. 5: Because of the danger of confusion and for storage reasons there is only one key-dimension for an unhardened (designation +C) or a hardened (designation: 55 HRC) or a quenched and tempered (designation: +QT +C) key dimension, but never two different designs from the same dimension at the same time. Marking of the keys is possible in individual cases, but too expensive for series production.The aim of the application is to check whether this risk of confusion still exists in reality during assembly or in storage, so this restriction can be dropped. On the development side, there is the requirement to be able to use certain keys with the same dimensions but different designs.