1. A cartridge comprising:a housing;a storage medium having an electrical contact surface; anda holder movable relative to the housing, the holder comprising:a first holder member including the electrical contact surface; anda second holder member engaging with the first holder member,wherein the holder has a through-hole through which an engagement part of the second holder member engaging with the first holder member is accessible from outside the cartridge, andwherein the through-hole is exposed outside of the cartridge.