Factual error: This film takes place in 1987, but when Norm Gunderson is talking to Marge about his paintings, he mentions a 29 cent stamp. 29 cent stamps weren't introduced until 1991.
Suggested correction: He mentions "who got" the 29-cents stamp, meaning a person's painting was selected to be on the UPCOMING 29-cents stamp. I don't know if it would take four years to actually manufacture a new stamp with a particular picture (painting), but this "planning" stage would more than likely mean that the 29-cents stamp was not yet (and would not be) available in 1987. Perhaps your entry could be more accurately classified as "other error" instead of "factual"?
Factual error: Several times during the highway scenes if you look closely you can see that some of the cars and trucks are early 90s models even though it's supposed to be 1986 or 1987.
Factual error: Per the opening credits, the movie is set in 1987, but when Carl leaves the airport parking garage, the billboard in front of him shows Northwest's "Bowling Shoe" livery which was not introduced until 1989.
