1-8 MPH treadmill for Stationary Exercise.  From “Directions for operating a Collins chain-compensated gasometer”, Second Edition Cat. No. P-469.  Warren E. Collins, Inc.  May, 1967.

“This sturdy, yet easily portable, 1-8 MPH treadmill moves on 5” dia. ball-bearing casters. The optional “Electrolift” enables effortless inclination to 16 degrees (30%) with only the touch of a switch.”