A system for reducing the risk of an incorrect selection or dispensing of a drug dose for use with a cartridge and a cartridge holder so as to prevent unwanted reservoir cross use. The coding system for use with the drug delivery device includes a first partial code feature and a second partial code feature. The first partial code feature and the second partial code feature cooperate to supply a combined visual indicator when the cartridge is assembled to the holder for indicating that a correct cartridge has been assembled to the holder.
