I was just browsing around the "Will the real 15 clone ..." and "the dark underside" threads and found a very similar machine. Caroline S has a machine badged "Mercury" that is almost identical - same bed decals, same "Dial-O-Matic" with "world best" badge, same foot pedal, same grape vine face plate, same motor mount, and same light mount on the belly of the pillar (these are the only two machines I've seen with this light mount). The differences other than "Mercury" vs "Illinois" is that hers has the name "Morse" stamped on the inside lip above the SN - mine does not, and her motor has a metal plate with "Morse" on it .. mine has no metal plate at all. Both of the machines have an SN that start with TA.
I can't wait to play with mine.