Here is an animated GIF showing Tom Landry, apparently during pre-game warm-ups:
Unlike the GIF I posted a few days ago, I do not know for certain the game from which this GIF was taken. It almost has to be from the 1971 season, though.
Two things to note:
(1) The goalpost is on the goal line, so the image has to be from before the 1974 season.
(2) The end zone has no art at all. From what I know, the only season in which no art appeared in end zone was 1971.
(a) A reader named Redmustang03 described the end zone art to me several years ago as follows:
The dark blue Cowboys logo with the helmet with two bars wasn’t put in until the 1981 season which lasted from 1981 to 1995 after the NFC championship game. Instead from 1972 to 1978, the Cowboys logo background was light blue with two white circles that included the Cowboys stars. In 1979 they did use the two helmets, but they were bigger in size and the background was still the light blue. In 1981, they changed the Cowboys words to Texas Stadium and used that for one year. After one year, they used the 1981 end zone logos until 1995 and the next year they have the aqua blue background with the Cowboys logo and the two helmets with the three bars. Until they switched from astroturf to field turf the Cowboys logo background changed to a dark blue not as dark as the 1981 logo and then put in the same two helmets with three bars.
(b) An image of Duane Thomas from the 1971 season clearly shows that no art appears in the end zone:
Any ideas about the date of the animated GIF?