Marlin has used both model, and serial numbers since they made their first handguns in 1870. However, this did not always include .22 rifles, as they were not always required to have a serial number, until 1968. Many Marlin .22 rifles from the post WWII to 1968 time were not serial numbered. Model numbers were always used, but some models were not marked with the model number. The model 1881, 1888, and 1889 Marlins were not marked with the model, but they were cataloged as these models.