 Complete the following phrase:  FN manufactured and marketed the Baby Browning from 1931 until 1979, though exports to the US only took place between 1953-1968. About 550,000 units were produced, including the hand chiseled engraved Renaissance and the Lightweight version. The Lightweight utilized a 6061 T6 aluminum frame and hexavalent chrome-plated over electro-less nickel slide and external detail parts. With the exception of special order nickel-plated units and the above-mentioned versions, all of the 1931 Baby Brownings were finished in chemical hot blue. The halt to exports to the US in 1968 was mandated by the Gun Control Act of 1968 - which was precipitated by 