cast iron union eagle & shield?

i know very little about this aside forom the obvious. it is an eagle holding what i believe is the union shield with 13 stars on it. on either side of the shield is a flag each having 8 stars. on the back is a spot that appears to have been the female end of a fastener it looks like it may have been threaded but it5 is hard to say because the male end was sheered off and remains in it. on the back as well the numbers 3335 are stamped. there is another mark on the back possibly a 3 or an 8 but more likely a blemish from the production process. it is just shy of 4" wide and again just shy of 3" tall with a depth of not more than 5/8" in the thickest spots.