The first one on the left was converted using a method that mimics the operation of a factory Micro. Builders used a factory pistol closed bolt on which they restored the lower lip of the bolt face to mimic a factory fully supported bolt face like that of a full auto Micro closed bolt, along with additional trigger housing mods as well. The one on the right used a method that was put into print in the form of a booklet called “Micro Uzi Machine Pistol semi auto modification manual” by Firepower Publications in the mid 80’s. It’s still available today in reprint from Delta Press online. This method was the least desirable way of converting the pistol as it required the fabrication of a complicated trip device, mods to the bolt, receiver, trigger housing, and elimination of the grip safety. Both are nice examples of the history of the methods used to convert these weapons to select fire back in the day.