These both appear plated. I am careful in my choice of words, but assertions have no place; I do not believe you can state the 1/2d is NOT plated.
I am somewhat of a specialist in both Victorian and E7 silver, but also love off metal strikes (OMS). The farthing is within tolerance on weight, the halfpenny is about 0.5 gm heavy compared to standard. However, the coin DOES appear heavily plated in the photograph with loss of detail secondary to this - a bit of blurring that I have seen often with heavier plating.
I will add that heavy plating may be "resistant" to non-penetrating assays/tests, including chemical, scratching, XRF. Specific gravity will pick it up & would anticipate with some likelihood that this 1/2d will register as near copper, but slightly higher. By quick memory, bronze is somewhere around 8.8-8.9 and sterling silver about 10.36-10.39.