Dan talks about using a crayon to draw on walls; crayons weren't invented until1903.
At about 1:10 while Don Murray is putting his shirt back on for dinner, the outline of his watchband is clearly visible on his left arm.
Alan Ladd injured his hand while working at his ranch during the lay-off in the March-April 1960 Screen Actors Guild strike against Hollywood studios, but was well enough to resume filming.