single barrel (Arogno) was introduced in the early 1960's . . . I would guess around 1960-62, but I am not certain.
so earliest 3-6-9-12 Master Times, which began in 1958, had the double-barrel movement . . . later 3-6-9-12s (say, 1960 through 1967) had the single-barrel. link below will take you to the Master Time chronology.
the double barrel guys are scarce, even more scarce are the double barrel guys that will run well.
thanks for the question.
jeff
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: HELLO ! On the master time, was the ARGNO 28
: single barrel movement used before 1967 on
: the early 3 6 9 12 models THANKS RONNIE.