Illinois Signamatic Power Reserve Model 9516. This is one of the only automatics produced by Illinois with (Swiss) manufactured movement. Movement is an ETA caliber 1256 with 17 jewels  with incabloc shock system. I believe they were produced between 1953 and 1955. Movement is time only with a 40 hour  power reserve indicator and is running perfect. Case is stainless steel with screw back and measures 31.6mm x 41mm overall. The band is unusual and marked KATY Railroad /Railroad Approved and has a brass KATY button affixed to it. The Illinois watch is not railroad approved  as far as I can tell but was original to watch when I acquired it.