The frame is made of Columbus "tenax" double butted chrome-moly steel tubing brazed at lugged joints.
It will not have date codes on the headbadge as I've learned this stamp coding was used on Japanese made frames. Your badge is likely (but who knows) original to the frame and reads "chicago" along the bottom.
Badge, design and Serial number Sc6...... tells me it is a Limited Production Schwinn frame made march '86 by a former school teacher named joseph* just before his lunch break.
Found some info on the googles that outlines how production of the Madison, along with a handful of other lightweight models, will move to Greensville plant for 1986.
Those decals are likely not correct according to the 1986 Schwinn catalog.
Anyway, cool bike; looks like a dope workshop.
*the story of Joseph the former school teacher was fabricated