Field Cross or Grave Marker

My mother bought this cross at a store called something like "Sacred Relics." They called it a Field Cross; it appears to me to be a grave marker of some sort. There is a flat area with holes that seems as though perhaps it used to have a plaque of some sort - perhaps the name of the person buried? We are very interested in finding out how old this piece might be, what it actually is, and what its value might be.

Fair