It is designed for testing compression in gasoline engines and is identified by manufacturer part number 28 2171.
New Vintage SEARS Flexible Drive Compression Tester Complete No. 28-2171 USA
New Vintage SEARS Flexible Drive Compression Tester Complete No. 28-2171 USA H1
VTG Sears Flexible Drive Compression Tester. Model # 161.217101.
Vintage Engine Vacuum And Fuel Pump Compression Tester Made In USA NICE RARE
Vintage RAC Compression Tester Made In USA Pressure