I have a platter that was given as a first place prize horse racing prize at Monmouth Park New Jersey. The platter is engraved July 12 1972 the date the race was run. The platter weighs about one pound 4.9 ounces. Engraved on the reverse is a Wallace logo,then WALLACE 1125. does anyone know if this is a silver alloy of some kind or silver plate? Thanking you in advance.