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:66, Page:495
SPECS: 6-1/2" (16.5cm) long.