You need to talk to an attorney who is versed in IL gun laws. Whoever told you that IL considers any gun over 100 yrs old as an antique and therefore nor longer a firearm is going to get you in some serious legal problems. Your premise is going to get you arrested and very likely charged with a felony.
"430 ILCS 65/1.1
Firearm means any device, by whatever name known, which is designed to expel a projectile or projectiles by the action of an explosion, expansion of gas or escape of gas; excluding, however:
(1) any pneumatic gun, spring gun, paint ball gun or B‑B gun which either expels a single globular projectile not exceeding .18 inch in diameter and which has a maximum muzzle velocity of less than 700 feet per second or breakable paint balls containing washable marking colors;
(2) any device used exclusively for signalling or safety and required or recommended by the United States Coast Guard or the Interstate Commerce Commission;
(3) any device used exclusively for the firing of stud cartridges, explosive rivets or similar industrial ammunition; and
(4) an antique firearm (other than a machine‑gun) which, although designed as a weapon, the Department of State Police finds by reason of the date of its manufacture, value, design, and other characteristics is primarily a collector's item and is not likely to be used as a weapon. "
The ISP has never made any such blanket >100 yr old ruling as described in (4). Any such exemption would be listed in the JCAR Admin Rules. Here's is the definition of an "antique firearm" per JCAR:
Section 1230.10 Definitions
“Antique firearm” means, for the purpose of 430 ILCS 65/1.1(4), any firearm with a matchlock, flintlock, percussion cap, or similar type of ignition system manufactured in or before 1898, provided it is not likely to be used as a weapon.
Your S&W .38 Lemon Squeezer does not fit the definition of antique firearm. Therefore, a FOID card is still needed to possess and concealed carry of it would still be a violation.
