Patek Philippe Hobnail Bezel Calatrava in 18k yellow gold on a 18k yellow gold mesh DA bracelet . With archive papers. Manual movement. Ref 3520. Circa 1974. Fine Pre-owned Patek Philippe Watch. Certified preowned Vintage Patek Philippe Calatrava 3520D watch is made out of yellow gold on a Gold Mesh band with a 18k Clasp buckle. This Patek Philippe watch has a 32 x 32 mm case with a Round caseback and White Roman Numeral dial. It is Gray and Sons Certified Authentic and comes backed by our 12-month warranty. Each watch is inspected by our certified in-house Swiss-trained watchmakers before shipment including final servicing, cleaning, and polishing.