I was mistaken. It a nickel stuck on quarter STOCK as per error-ref http://www.error-ref.com/wrong_planchet_and_off_metal_errors/
I think they are WELL aware of that. Some will pick at the silliest stuff, and not answer the Q........
there are several more examples for a "wrong planchet" nickel other than being struck on dimes and quarters. There are lots of other options for a nickel to be on the wrong planchet other than just nickels and dimes. Foreign planchets (The Philippines), 1 cent planchets, $1 planchets, and foreign objects (steel washers), to name a few...