The various trials in the 1950s were long before the XM9 trials in 1979-1980, and then again in 1984, so its apples and oranges. Beretta only had the Model 1951 at the time the 1950's trials, and I don't believe it was entered.
In regard to the XM-9 trials, the S&W 459 was the S&W entrant in...