Vintage brass Waltham pocket watch

I lost my vintage brass Waltham pocket watch yesterday around 3pm. It's a collector's piece, about 4 cm in diameter, with a white enamel dial, Roman numerals, and a short silver-tone chain. The case is brass with a subtle patina and the back is engraved with the initials 'P.K.' in a small flourish. I was near Winchester Cathedral's The Close, then wandered down College Street toward The Guildhall Market, and I think I might have dropped it near the Bookshop on High Street or outside the post office near Market Place. This watch has sentimental value—my grandfather wore it for decades—and I really need it back.