https://collectability.com/learn/a-collectors-guide-patek-philippe-ref-5004-split-seconds-perpetual-calendar/
A COLLECTOR'S GUIDE: PATEK PHILIPPE REF. 5004 SPLIT SECONDS PERPETUAL CALENDAR - Collectability
Jan 28, 2026 - In 1994, Patek Philippe introduced a pivotal reference in its legendary perpetual calendar chronograph lineage: the ref. 5004, which added split-seconds...