One of approximately 900 manufactured and registered with the BATFE in the early 1980s, these S.W.D. Inc. Auto Connectors were, and still are, one of the most cost effective ways to make an AR-15 platform rifle fully automatic. This example is marked "S.W.D. ATL. GA. M.15A.C./PAT. PEND." followed by the hand marked serial number "AC170". With an extra bolt contact arm and other small parts.