Abstract: A cartridge magazine for firearms comprises a key insertable through a slot in the end panel of the magazine for engaging the spring engaged elevator upon which the shells are supported. The slot includes a series of transverse or lateral branches spaced longitudinally on the panel for receiving the key and locking the elevator in position. The magazine thus may be loaded with cartridge shells in stages as defined by the lateral locking branches. After loading is completed, the key may be removed from the magazine and clip so that the latter may be inserted into the firearm with which it is used. In an alternatively preferred embodiment, optional marking means are positioned on top of the magazine for placing an identifying marking on each cartridge shell.