Mid-century link Patek Philippe world timers are known to exist in yellow white and rose gold cases but all link three Eurasia models now known to exist are all yellow gold and all appear with as link reference 2523 models. If you struggle to tell 2523 and 2523-1 watches apart from one another the lugs are an easy-to-spot tell. You'll see on this watch that the lugs overlap the case in a dramatic fashion while the 2523-1 lugs appear more flush to the case.