Nice job and welcome to the forum. That's a find you'll never forget. Looks like the one I have. Post a picture of the back and I'm sure someone can give you some info as to type. I think the one I have is called a puppy paw. I'm still learning but there are many experts on this site. Hunt that place hard and good luck.
Nice plate johnnyrum and welcome! It looks like you have a US Cartridge Box Plate. The 4 rusted spots on the back are where the iron hooks were that attached it to the Cartridge Box. Excellent find.
SAY WHAT ? THIS IS A NEW TNET MEMBER AND HE HAS SCORED BIG TIME ALREADY . HERE I HAVE BEEN DETECTING SINCE 2007 AND HAVE YET TO FIND A BOX PLATE CONGRATS MY FREIND CONGRATS AND WELCOME TO TNET FOR U WILL FIND MANY INTERESTING PEOPLE ON THIS SITE.