Lyman introduced the No. 17A Globe Target Front Sight circa 1929 as an improvement over their No. 17 front sight.  This No. 17A front sight included seven interchangeable inserts that were locked into place with its threaded cap.  This sight became such a huge success that Lyman added a couple extra insert options in 1931 and 1933 and eventually discontinued its predecessor, the No.17 front sight, by 1938.  This No. 17A front sight has enjoyed over 80 years of production and continues to be a popular item today.