Blast from the past accurized 1911 by R.L. Shockley

[diopter]

http://tonybrong.########.ca/2012/08/richard-l-shockey.html

Picture of his "mousetrap" on the recoil spring lug to tighten up the front of the barrel.
http://4.bp.########.com/-uCLEes4clDs/UDVG5eBcw1I/AAAAAAAABuM/bnj7BgUOS8I/s1600/Shockey+mouse.jpg