Anyone see this before? http://www.freepatentsonline.com/4597211.pdf

It's an inertia activated rear sight that theoretically makes it unnecessary to regulate a double. I can see all sorts of shortcomings, most revolving around the tiny intricate parts to some degree. Also, given that most doubles are two trigger / extractor propositions specificly to avoid problems with such delicate parts, even more delicate ones working on the same principal aren't likely to find much favor. I may see some advantage for the man who would like to ocassionally shoot slugs in a shotgun but for a rifle??? Well, it is interesting any way.