Hell House - S1-E17
Revealing mistake: Dean gets his phone and snaps a picture of Sam when he's asleep. You see his phone take the picture but the screen is then white, showing he didn't really take anything.
Revealing mistake: During the love scene between Dean and Cassie, you can see the tape used on Cassie to keep the show PG-13. (00:23:15)
Revealing mistake: When Sam pulls Angela out of the bathtub and on to the floor, you can see the panty line from the nude colored panties she's wearing to keep the show PG13.
Revealing mistake: When Max opens the bedroom door to confront his step-mother and Dean, using his telekinesis powers, you can see the equipment used to open the door, a rope pulling the door on the floor. (00:34:19)
Answer: Angel blades come from angels. It's their angelic magic that makes it special. Therefore, an archangel blade is made magical with the powers of an archangel. They couldn't have just created one or used one, as none of them are archangels.