This is a vintage brass feeler gauge (also called a thickness gauge or gap gauge) used by mechanics.
Each prong is a different precise thickness (measured in thousandths of an inch or millimeters) for checking and adjusting tiny gaps in engines — such as valve clearance, spark plug gaps, or ignition points.
Before digital tools, these brass sets were essential in every garage and workshop. The numbers correspond to specific gap sizes, making it easy for mechanics to work accurately.
These tools were common from the early 1900s through the mid-20th century. Finding one today is a cool piece of automotive history!
