You can always tell when period pieces were filmed by looking at the women's hair, and to a lesser extent, the men's.

I always laughed at the blow-dried 'dos on Little House on the Prairie.

Black Sheep Squadron had the 70's hairdos too, along with the very tightly tailored uniforms on the men. WW2 airmen never looked like that.

I can't remember what show it was, during the 80s, when WWII soldiers had mullets.

The weird ones, are the "mashup" movies and shows, like Streets of Fire, and Reprisal.