I was getting ready to order a metal safety button kit for my Mossberg 500 HD when I suddenly noticed for the very first time that I already had a metal button. Now my question is: is this stock or add on? Does anybody out there have an older Mossberg 500 with the metal button from the factory? And if so, does anybody know when they switched to plastic? See button below. It isn't current add on safety as sold on the internet. Front of the button is smooth and all the add ons have serrated fronts.