Wild, Wild West oops.

[Baltimore Ed]

Watched a couple of Wild, Wild West episodes and in a rare outdoor shot saw contrails in a blue sky. Used to come home from school and catch an episode every day. I understand it?s not a Ford film but I?m always looking for slip ups in tv shows or films. Watched a B horror film once and in one scene the policia victim?s handgun changed from a revolver to a 1911.

[Major 2]

It is easy to spot firearms out of time period so prominent in so many films its not even sport.
50 star US flags in WW2 or earlier films ? Newer cars in vintage period shots or AC units in windows , power lines 
....I often catch wrist watches on extras

Usually there is just one continuity person on a crew especially on locations stuff does get by that just cant be foreseen....

Like contrails ( as you mention ) or the pickup truck in John Wayne's " Alamo "  and the white car in Braveheart 
The wake of the film boat  or the tire tracks in chase shots in Westerns.