06/26/2026
Relatable dilemma for watch collectors: WHICH AP PERPETUAL CALENDAR SHOULD I CHOOSE?!?!
Personally, we see this a champagne problem. Either way you're getting an exquisite timepiece BUT there are some differences.
The OLD 26574ST uses the Calibre 5134, which has the classic perpetual calendar layout with week indication, day, date, astronomical moon, month, leap year, hours, and minutes. AP lists it at 41mm x 9.5mm, 20m water resistance, 40-hour power reserve, 374 parts.
The NEW 26674ST uses the newer Calibre 7138, which is the upgrade. It keeps the same 41mm x 9.5mm Royal Oak case profile, but bumps water resistance to 50m, raises power reserve to 55 hours, runs at 4 Hz, and most importantly, lets you adjust the perpetual calendar entirely through the crown instead of using little case-side pushers/tools.
From a collector/dealer perspective, the 26674ST is the “better watch” technically. It is more user-friendly, more robust, easier to set, cleaner on the case-side, and has improved water resistance. AP specifically redesigned the system so the user can correct the watch without tools and with less risk of damaging or desynchronizing the movement.
The 26574ST may still be more appealing to some collectors because it represents the previous era of AP perpetual calendars and uses the Calibre 5134, which itself came from the old ultra-thin 2120 lineage. The 26674ST is more modern & the 26574ST is more “old AP DNA.”
My simple buying take:
Buy the 26674ST if you want the newest, most practical, technically improved Royal Oak Perpetual Calendar.
Buy the 26574ST if you want the older-generation feel, prefer a specific dial variant like the earlier color configurations, or can get it at a meaningful price advantage.
