This tool is used to safely remove and replace the firing pin stop from 1911 style slides.
Instructions To Replacing The Firing Pin Stop
Position the firing pin stop in the proper retaining slot (stop styles are printed on side of tool). Depress the firing pin with the notch on edge of tool. Slide the stop into groove until end of tool meets top of slot in frame. Tilt the back end of tool down and continue pushing the stop until the tool stops on the slide and the firing pin enters the hole in the stop.
1911, Issue:11, Page:058
Big Book Catalog, Issue:68, Page:153