When Doc Griffin reaches for the ointment the jar has a lid. In the next scene you see him pulling his hand back with the jar but the lid is gone.
When Smiley's head is chopped off, he is holding two 5-shot Freedom Arms Model 83 pistols, for a maximum of 10 rounds without reloading. He fires at least 24 shots before he falls over.
General Custer and Mark Twain talk about the Sequel to Tom Sawyer, "Huckleberry Finn", but that book wasn't even written until 1885, ten years after this movie's time-line, and nine years after Custer's death. In 1875 "Tom Sawyer" hadn't even been published yet ... that wasn't until 1876. (As well as that, Samuel L. Clemens (aka Mark Twain) was only 40 years old in 1875, and still had brown hair.)
Abner Doubleday did not invent professional baseball.
Little Pete eats an ice cream cone, which was invented at the 1904 World's Fair in Saint Louis, Missouri...Ice cream was INTRODUCED at the World's Fair. Ice cream in many forms dates back a few millennium to various countries in many iterations. It was made in this country via churn, etc, into the 1800's.
Ramon describes tacos to his brother Pete as having crispy shells. Hard-shell tacos were invented in the late 1940s.
General Custer died in 1876. The Prince and the Pauper was published in 1881.
Abraham Lincoln was shot April 14,1865, and died the next day. According to the movie Danny was his bodyguard at the time. Peanut butter was patented in 1884. Unless Danny has not aged in 19 years, peanut butter should not exist in the movie's time frame.
Patch refers to Clem's eye as "going round and round like a tassel on a stripper's dirty". Pasties did not rise to prominence until the 1920s with tassels first being added in the late 20s and early 30s.
Smiley uses two Freedom Arms model 83 pistols during his death scene. Freedom Arms was founded in 1978.