Developed in the 1960s, the short-lived Spitfire Carbine was an open bolt semi-automatic weapon that was found by the ATF to be readily convertible to full automatic by at least four different methods, including fiddling with the safety to make the disconnector malfunction and disabling some small internal parts. Retroactively declared a machine gun, most Spitfires were destroyed by their owners, with a limited number registered per the NFA. In appearance the Spitfire is made to look like the famous Thompson SMG, though the core action is essentially a tube gun version of the M3A1, including compatibility with the M3A1's magazines. Blade front and peep rear sights, with a set of alloy pistol grips, manufacturer markings on the magazine well (with the original "SEMI-AUTO" marking modified to read "FULL-AUTO", and a fixed buttstock. Internally, the disconnector has been milled down for a permanent conversion to full auto operation, with the safety switch unaltered.