The item is most assuredly a contemporary cast reproduction of a South Carolina hat pin. The original military hat pins of the 1850's and 1860's (including ones such as the South Carolina palmetto tree design), were stamped from thin rolled sheet brass. On the original thin stamped brass South Carolina hat pins, the palmetto tree trunk just below the palm fronds is a very weak point, resulting in most original found specimens being broken and separated into two pieces. With thin rolled sheet brass that is die stamped, the design impression is also seen in reverse relief, on the back side. On military accoutrement devices that were more utilitarian and subject to stress and strain, lead solder fill was poured into the back of thinly stamped brass items, for products such as belt plates, cartridge box plates, etc., to produce a stronger finished product. Lead solder fill though, was almost never used (with rare exception), on thinly stamped brass headgear insignia. A quick, "at a glance" inspection of the back on this piece above, shows no reverse impression detail, of a stamped South Carolina palmetto design. The back side of this particular SC palmetto hat device, clearly shows the smooth surface and flow lines, of cast material. Additionally, the curious scratching marks (where obviously someone recently "tested" to see what type of metal was present), clearly shows brass and rules out any other fill material. Cast reproduction hat device pieces, have been available to reenactment groups over the past four decades or so, and are on occasion found in proximity to noted Civil War battlefields.
An original South Carolina palmetto tree hat pin device is in my personal collection, excavated in a camp of the South Carolina Artillery, among many South Carolina buttons, and Civil War period coins.
CC Hunter