From the very beginning, the Superposed was availble in the four grades: Grade I, Pigeon Grade, Diana Grade and Midas Grade, up to WW-II. When production resumed after WW-II, they got the A5s going first. The Superposed Grade I in 12-gauge was reintroduced in 1948. In 1949 the Grade I in 20-gauge was added to the line. In 1950 the better engraved models were added to the offerings in Grades II (similar to pre-War Pigeon), III, IV, and V (Similar to pre-War Diana). In those early post-War years, the 26 1/2 inch barrel guns were called Lightnings, the 28-inch Field and the 30-inch 12-gauges Trap. Also, in a few flyers, the 20-gauge was called Blue-Streak. It wasn't until 1956 that the true Lightnings were again offered. On July 15, 1957, Browning announce the addition of a Grade VI to the offerings at $1000 in standard weight and $1015 in Lightning. In the December 1960 Browning Catalogue they began using the Pigeon, Pointer, Diana and Midas Grade designations, but the guns actually pictured were the old Grades II, III, V and VI. By the December 1961 catalogue the new engraving patterns were accurately pictured.
I don't see that Ned says anything one way or the other about the twin single triggers.