The only Royal Oak Extra-Thin in yellow gold is a limited edition of just 50 pieces. We take a look, with original photos and pricing. Most of the gold watches sold are 18k rose, pink or red gold. A quick once-over of a catalogue proves that. Yellow gold is slightly out of fashion. Cheap replica Audemars Piguet watches is the first amongst established, high-end watchmakers to emphasise the metal, with a full range of yellow gold Royal Oaks presented at SIHH 2016, including a chunky chronograph. Last year, however, Audemars Piguet announced arguably the most interesting yellow gold Royal Oak of all, a limited edition made for Singapore retailer The…