I thought it looked alot like a Heavy-Duti. Seller sent me a pic of the chain guard. Says it's a "Supreme". Not sure if it's a dept store Schwinn or bike shop Schwinn.
A summit built heavy duti from the 90s when the Schwinn signature series was built. Not Chicago of course but remember all the repops? well this is the heavy duti redo. Signature series or these bikes with the S on them someplace were more bennis than your standard wally world ones and were sold at performance bike and other random places.