chicago steel.

As a testament to innovation in American manufacturing, Schwinn's early frames were constructed using a proprietary process called electro-forging, where a high electrical current was passed through two pieces of steel as they were simultaneously pressed together.  The frame is a monolithic piece, not a series of tubes welded together.  The process and the machinery have since been lost to time.

The geometry of this particular model mimics early english 3-speeds.  The internally-geared rear hub has been completely rebuilt,  and is essentially maintenance free.  The wheels have been laced with modern aluminum rims for a smoother ride.

The design was available only a limited number of years.  Soon after, as the market was influenced by European endurance racing, the posture became much more aggressive.  It would be nearly 50 years before upright geometry would make any significant return to the US market.