Illinois has a tougher than most law in that they place the removal/obliteration of ANY manufacturers markings (maker, model, ID numbers,etc) in the same class as a serial number removal/obliteration alone. Both the act of doing so and the possession of the defaced firearm. I personally wouldn't mess with that one. Just a big problem waiting to happen IMO.
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(720 ILCS 5/24-5)
Sec. 24-5. Defacing identification marks of firearms.
(a) Any person who shall knowingly or intentionally change, alter, remove or obliterate the name of the maker,
model, manufacturer's number or other mark of identification of any firearm commits a Class 2 felony.
(b) Possession of any firearm upon which any such mark shall have been changed, altered, removed or obliterated
shall be prima facie evidence that the possessor has changed, altered, removed or obliterated the same.