The three main action designs for break open double guns are; sidelock, boxlock & trigger plate. A boxlock does not have to be of Anson Deely design to qualify as such. There were even muzzle-loaders well before Anson & Deely which were called BoxLocks because the firing mechanism was placed "In the Box" (Frame) rather than on a side plate.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra