Factual error: Lucas is wearing a pair of jeans with a large "W" stitched on the right back pocket. These are Wrangler jeans, which first went on sale in 1947. "The Rifleman" is set in the 1880s.
Revealing mistake: Two former Civil War officers prepare to make camp in a sandy area surrounded by large rock formations. It is obvious that they are on an indoor set. As one man takes a few steps, the sound of his boots hitting the wooden platform beneath the sand can be heard.