To obtain a printer in which use of a counterfeit of an ink ribbon or a roll of print medium can be inhibited, and to obtain a roll.

The printer includes a roll holding part which holds a roll constituted by winding a strip to which an invisible identifier is imparted, an irradiation part which irradiates light toward the strip of the roll held in the roll holding part or the strip fed out from the roll, a light receiving part which receives the light coming from a region of the stripe including the identifier when light is irradiated from the irradiation part, an identification part which identifies the identifier based on the light reception results from the light receiving part, a control part configured to change a predetermined setting or operation or to perform a predetermined setting or operation according to the identification results from the identification part, and a print part configured to print on a print medium included in at least one strip.