Since annular container flange 18 has a downwardly sloped upper annular surface to act as a cam surface and annular lower portion 38 is resiliently hinged, passage of annular lower portion 38 thereover is facilitated without the realization of {HEAD ~ great stress} in {TAIL ~ annular frangible area} 28 
Since annular container flange 18 has a downwardly sloped upper annular surface to act as a cam surface and annular lower portion 38 is resiliently hinged , passage of annular lower portion 38 thereover is facilitated without the realization of { HEAD ~ great stress } in { TAIL ~ annular frangible area } 28
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