Section 5-142 - Removal or alteration of identification mark or number on firearm(a) A person may not obliterate, remove, change, or alter the manufacturer's identification mark or number on a firearm.(b) If on trial for a violation of this section possession of the firearm by the defendant is established, the defendant is presumed to have obliterated, removed, changed, or altered the manufacturer's identification mark or number on the firearm.