This is the second movie in which Glenn Ford (Marshal Dan Blaine) has his gun buried in a grave after a shootout at the end of the movie. The first was La pistola sepolta (1956), in which he played George Temple, a soft-spoken storekeeper.
McGuire was able to tell Squint was cheating in the poker game because the game was "jacks or better" for openers, and Squint showed a straight flush in clubs, ace through five, after drawing one card. To open the pot, Squint had to have a pair of aces in order to qualify to open, as his other cards were too low, and therefore had to have discarded an ace to draw his one card. But McGuire had three aces, so Squint could not have had the necessary two aces to open, so he was cheating. The other players commented that they too wanted to see Squint's openers, so they too suspected something fishy.