Found this button a couple of hours ago in the backyard next door. We had dug up a lemon tree there for replanting last year it was in that area. It was down about 8 inches, the Vaquero gave a strong signal in the loose sandy soil. Look carefully you can see the eagle and the D in the center shield which indicated Dragoons.
I've added a second picture with a better angle to see details.
I've added a second picture with a better angle to see details.