Be it Ever So Mortgaged - S1-E2
Revealing mistake: When Gladys is looking through the window, you can see part of the facade cross bracing.
I, Darrin, Take This Witch, Samantha - S1-E1
Revealing mistake: After the hairbrush comes to Samantha, she starts to brush, and you see the lights reflect off the wires used for the gag.
Answer: The original diamond and white gold heart necklace was given to Elizabeth Montgomery by her then real-life husband, William Asher, who also directed the show. She wore it in nearly every early episode. When the necklace was lost or stolen about mid-way through the series, Montgomery had two replicas made from rhinestones. She wore either one of those for the rest of the show's run.
raywest ★