[ithacaartist]

Sure, Glenn, this part is called the "holdopen", which, when the last round is gone from the mag, is pushed up by the mag's follower button in its top position. When this occurs, the wedge-shaped portion on the back end of the part engages the underside of the breech block, holding the action in the open position until the empty mag is removed and the toggle knobs are drawn back and released, with either no mag or a loaded mag, and the action will return to battery. It's one of the numbered parts, and should have the last two digits of the Serial# stamped on it.