No person shall wilfully or maliciously 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 or registration card during any time in which such license plate, seal or registration card is operative. 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 said number is illegible or insufficient for identification purposes. (Ord. 189; amd. Ord. 412, 7-10-1967)