Field Cross, or grave marker?

My mother bought this cross a few years ago from a store called something like "Sacred Relics" in downtown Oklahoma City. They called it a field cross. It looks like a grave marker to me. It has a rounded area near the bottom where it appears that there used tob be some sort of plaque - possibly a name? The top says "RIP" and there is a plaque made of what appears to be metal near the top of something that looks perhaps like a saint. The entire front is heavily engraved and the back is flat. It it very heavy and made of some sort of metal. We are very curious as to what it actually is, and what it's value might be.