Early Colt AR-15 Select Fire Model 604 Custom. This Colt factory select fire AR-15 Model 604 is one of possible only a few existing examples released for non-military or collector use. The few domestic pieces that may exist are unique in that they have no roll-stamped "PROPERTY of US GOVT" on the lower receiver. What further sets this example apart is that there is no model designation present (602 models), nor is CAL. .556 present (604 models), instead the lower receiver is marked Colt AR-15, CAL. .223 with the serial number. Discussions with Colt, and the provenance of the collection from which this gun came point to a special one-off build for a Colt Executive. The production date is most likely late 1963 early 1964. This unique factory select fire, early model Colt AR-15 is in excellent condition, one of only a handful of known examples.