They made thousands of them. They destroyed most of them before they were issued. Some seem to have escaped the destruction. Back in the seventies I saw one of those in Ed Karrer's Gunatorium. He actually had a couple of them installed in mint 1903 MkI rifles hanging on the wall behind the customer counter. I loved that shop. It was like Lever Arms on Steroids. Besides the two in rifles there was another two under the counter that you could get a close look at. I offered to purchase one of them but there was no way Ed would part with them. It seems he managed to get them from a National Guardsman in a trade. He also had a case of ammunition and spare magazines. I wonder if the device in the video was one of those???
IMHO the reason they were destroyed was to promote the development of sub machine guns. If those were left available the Army/Marines would make do.