This really does not look like it has been used much at all. Since I really have no way to test this, it is sold as is.
Vintage RAC Rotating Dial Engine Compression Tester Original Box Manual F3.5
Vintage RAC Rotating Dial Engine Compression Tester #1535 Original Box USA 224
Vintage RAC Rotating Dial Engine Compression Tester Seal-Kwic Model 1539 EUC
Vintage RAC Rotating Dial Engine Compression Tester Model 1539
Vintage RAC Rotating Dial Engine Compression Tester PSI Untested
Vintage RAC Rotating Dial Engine Compression Tester Original Box Manual 1535