One of the rarest versions of the Thompsons Submachine Gun is the Model of 1927 Thompson Semi Automatic Carbine. These were regular 1921 machine guns that had their fire control groups slightly modified to only firm in semiauto and their receivers remarks to show Model 1927 instead of 1921. The rationale was a number of requests Auto Ordnance received from potential customers who wanted the look of a Thompson, but not an actual machine gun - mostly police and prison agencies that did not want to entrust their officers will fully automatic arms. Only about 100-150 1927 model guns were sold (and there is no specific serial range, they were simple converted one at a time as ordered). Of that very small number, only a very small percentage survive intact today, as most were converted back to fully automatic by later owners. Note that because the receiver is basically identical to a standard Thompson SMG receiver, these are considered machine guns under US law despite being factory semiauto carbines. However, this does mean that they can be legally converted to fully automatic (as, in fact, most have been).