While it may not be a mistake, The Publicist says to Journalist, "Foes in '76, friends in '85," but when The Journalist repeats it to The Legend Maker, he says, "Foes in '75, friends in '86."
Sitting Bull joined Cody's show in 1885. The performing arena shows several Wyoming state flags, but Wyoming wasn't granted statehood until 1890, and that flag wasn't adopted until 1917.
There is a flag on the flagpole. All 3 flags have 48 stars on them. The flag with 48 stars didn't come about until 1912.
Another flag with 48 stars is seen just prior to the Presidential scene. When Buffalo Bill plays for the President, the Presidential booth is adorned with two flags, each with 48 stars. The 48-star flag became the official flag in 1912.