Accurate Comparison Measurements For All Gauges
Made to our special order so gunsmiths can measure metal removal when working on shotgun bores. One end is inserted into barrel and opened to maximum. Other end is measured with regular mike to get information desired. A difficult tool to make because of extremely critical center-to-end tolerances.
Big Book Catalog, Issue:70, Page:472
SPECS: 6-1/2" (16.5cm) long.