A good late 18th Century officer's sword

A good late 18th Century officer's sword, curved blade 27 in., gilt brass stirrup hilt with fine border and leaf engraving, back strap engraved with two entwined snakes, wire bound fish skin covered grip, gilt brass mounted leather scabbard, the chape engraved 'DUDLEY/ GRAND PARADE/ PORTSMO.' all encircled by a snake eating its tail, possibly for a naval surgeon.