No person wilfully or maliciously shall remove, destroy, mutilate, or alter the number of any bicycle frame licensed pursuant to this chapter. No person shall remove, destroy, mutilate, or alter any license plate, seal, or registration card during the time in which the license plate, seal, or registration is operative. However, nothing in this chapter shall prohibit the Police Department from stamping numbers on the frames of bicycles on which no serial number can be found or on which the number is illegible or insufficient for identification purposes. (1979 Code 75.26)