Well Woooooo Hoooooo ! I think this is the FIRST in the Gallery to showcase Illinois "Tiny Dies" which were originally used on ALL Special Plates and Temporary Special Event Plates which are valid only for a few months. (Illinois is the only state to have Valid Special Event License Plates). Now these dies are only used for County Sheriff License Plates, with format S##(#)-###. After S is a number from 1-102 which is a Numeric County Code done by Alphabetical Order of the County Name, similar to Alabama and Nebraska. Of course you can still find these on Old Specialty License Plates, but it's pretty rare to see today, even over here ! And just like in your case, it's mostly found on the Front License Plate !
Lol notice the State Name is Left Justified and not all capital like the Old School Blue Stripe 1982 License Plate of which was the Standard when this plate came out ! This was one of the First Illinois Special Plates, part of the Original Collection... I remember seeing it in 1997 possibly older than that...