No person shall lawfully or maliciously remove, destroy,
mutilate or alter the number of any bicycle frame licensed under this
article or remove, destroy, mutilate or alter any license plate, seal
or registration card issued under the licensing provisions of this
article. Nothing in this article shall prohibit the Police Department
from stamping numbers or other identification on the frame of a bicycle
to be licensed on which no serial number can be found or on which
the numbers are illegible or insufficient for identifying purposes.