nˈaɪntiːnhˈʌndɹɪd sˈɪksti sˈɪks nˈaɪntiːnhˈʌndɹɪd sˈɛvənti θɹˈiː: ðiːz mˈɑːdəlz hæv stɹˈɪps ʌv mˈɛɾəl wˈɛldᵻd ˌɪntʊ ðə ɹᵻsˈiːvɚ ænd mˈætʃɪŋ kˈʌts mˈeɪd ɪnðə "sˈiː" tɹˈɪɡɚ ɡɹˈuːp tʊ ˈoʊnli ɐlˈaʊ ðɪ ɪnsˈɜːʃən əvən "sˈiː" tɹˈɪɡɚ ɡɹˈuːp.
(1966–1973): These models have strips of metal welded into the receiver and matching cuts made in the "SE" trigger group to only allow the insertion of an "SE" trigger group.