Really tough to tell from the photos. The face photo looks right for brass/bronze and looks quite old to me, while the rear photo looks to have corroded like pot metal (zinc, tin) does, in big chunks and voids around the edges. The bronzy color on the rear “damage” isn’t right for pot metal though, which corrodes white. Could be physical damage to brass, plus dirt, causing a resemblance to chemical damage (corrosion) to white metal. Just tough to say, not being familiar with your soil characteristics, and with the fuzzy pics. Lightness points to pot metal.. but that’s subjective. You could use a knife and/or plumbing torch to remove and test a bit on a damaged edge, reduce it to its native color by shaving or melting.
