A system of marked medical containers comprises at least two containers having different properties in at least one respect, and at least one machine-readable marking on each of the containers, each marking being designed to allow discrimination between the difference in properties. Each marking allows discrimination between the difference by having at least one area with different absorbence or reflectance when irradiated with radiation in non-visible frequency ranges. A specific container comprises a syringe cartridge type container for use with a preparation delivery device.