BBS Factory AP Royal Oak 26574ST Perpetual Calendar Technical Guide
The BBS Factory Royal Oak Perpetual Calendar is based on Ref. 26574ST.OO.1220ST.01, combining a 41mm stainless-steel case with a blue Grande Tapisserie-style dial and a multi-display perpetual-calendar configuration.
According to the supplied specifications, the BBS version measures approximately 41mm in diameter and 11.4mm in thickness. It uses a modified automatic movement based on the Miyota 9015 architecture with Calibre 5134-style visual construction.
The technical interest of the 26574ST extends beyond its Royal Oak case design. Its dial integrates multiple calendar indications, including the day, date, week, month, moon phase and leap-year information.
41mm Stainless-Steel Case
The BBS 26574ST uses a 316L stainless-steel case with the angular case and integrated bracelet architecture associated with the Royal Oak design.
The supplied dimensions are:
Case Specification BBS 26574ST
Diameter 41mm
Thickness Approx. 11.4mm
Material 316L Stainless Steel
The 11.4mm thickness is particularly relevant on a watch containing several calendar indications and a modified automatic movement.
The exterior combines multiple surfaces across the octagonal bezel, middle case and integrated bracelet, making the transitions between brushed and polished areas important visual details.
Blue Grande Tapisserie-Style Dial
The blue dial uses a Grande Tapisserie-style geometric pattern surrounded by multiple calendar scales.
Applied hour markers and faceted hands contain luminous material, while the calendar information is distributed across several displays.
The dial combines:
- Hours and minutes
- Day
- Date
- Week indication
- Month
- Moon phase
- Leap-year indication
Because several indicators share the same dial, their positioning and readability are more important here than on a conventional three-hand Royal Oak.
Perpetual Calendar Layout
The perpetual-calendar-style layout is the defining technical feature of the BBS 26574ST.
Rather than displaying only the current date, the dial organizes several different calendar cycles simultaneously.
The day, date and month provide the conventional calendar information, while the week and leap-year indications add additional calendar data.
The moon-phase display provides a separate astronomical indication.
These functions should be understood as parts of a connected calendar system rather than independent decorative subdials.
Day, Date and Month Displays
The day, date and month indications form the core of the calendar layout.
Their individual scales and indicator hands allow several calendar values to remain visible simultaneously without relying on conventional date windows.
For this type of complicated dial, alignment is particularly important because even small differences in pointer position can be noticeable against the printed scales.
Week Indication
The additional week indication expands the amount of calendar information available on the dial.
This is a useful characteristic to document with high-resolution photographs because it can be difficult to distinguish in conventional product photography.
It also helps differentiate the 26574ST calendar architecture from simpler complete-calendar configurations.
Leap-Year Indication
The leap-year indication represents the four-year calendar cycle associated with a perpetual-calendar mechanism.
This is technically important because leap-year calculation is one of the characteristics separating a perpetual calendar from simpler annual or complete calendar systems.
For the BBS version, however, its mechanical implementation should be understood according to the modified movement actually installed rather than assuming that its internal construction is identical to an original Calibre 5134.
Moon-Phase Display
The moon-phase display forms one of the most visually distinctive parts of the 26574ST dial.
Beyond its appearance, it functions as part of the watch’s calendar information.
Important details include the moon-phase disc, aperture geometry and its relationship with the surrounding calendar displays.
For an individual watch, actual moon-phase operation can be documented separately in the corresponding QC test.
Why the Perpetual Calendar Matters
A perpetual calendar is mechanically more complicated than a conventional date display.
In principle, a perpetual-calendar mechanism is designed to account for different month lengths and the leap-year cycle when the calendar remains correctly set and the movement continues running.
For the BBS 26574ST, however, the behavior and adjustment sequence should be evaluated according to its specific modified movement.
The presence of the same calendar indications does not mean that its internal architecture is identical to the original AP mechanism.
This distinction is particularly important when comparing complicated replica movements.
Calendar Adjustment
Multiple calendar indications interact within this configuration, so calendar adjustment should follow the correct sequence for the installed movement.
Individual calendar displays should not be force-adjusted without understanding their interaction and the movement’s calendar-change period.
This is especially relevant when adjusting the day, date, month, leap-year and moon-phase indications.
For a complicated mechanical watch, knowing the correct adjustment procedure is more useful than simply knowing how many complications appear on the dial.
Sapphire Crystal
The supplied BBS configuration uses a sapphire crystal with anti-reflective treatment.
This is particularly useful on the 26574ST because the dial contains multiple scales, calendar hands and subdials.
Anti-reflective treatment can improve visibility under certain lighting conditions, but it should not be interpreted as eliminating reflections completely.
9015-Based Calibre 5134-Style Movement
The movement is one of the most important technical details of the BBS 26574ST.
According to the supplied configuration, it uses a Miyota 9015-based automatic movement modified to reproduce a Calibre 5134-style layout and appearance.
For technical classification, it is more accurate to document the movement as:
Base Movement: Miyota 9015
Movement Type: Modified Automatic
Visual Architecture: Calibre 5134-Style
This is more informative than simply calling the movement a “5134.”
9015-Based vs Calibre 5134 Architecture
The BBS movement should not be confused with an original Audemars Piguet Calibre 5134.
The BBS configuration starts with a different underlying movement architecture and is subsequently modified for the calendar functions and Calibre 5134-style visual presentation.
This distinction can affect several technical characteristics, including:
- Movement construction
- Calendar mechanism
- Adjustment procedure
- Component layout
- Servicing
- Power reserve
- Movement performance
Specifications belonging specifically to the original Calibre 5134 should therefore not automatically be assigned to the BBS movement.
Automatic Winding
The BBS configuration uses an automatic mechanical movement.
Rotor movement provides automatic winding during normal wear, while the movement architecture supports the multiple calendar indications displayed on the dial.
The visible rotor and movement finishing should be considered separately from the underlying 9015-based architecture.
Visual similarity does not by itself establish identical mechanical construction.
Technical Specifications
Specification Details
Factory BBS Factory
Reference 26574ST.OO.1220ST.01
Collection Royal Oak Perpetual Calendar
Case Diameter 41mm
Case Thickness Approx. 11.4mm
Case Material 316L Stainless Steel
Dial Blue
Dial Pattern Grande Tapisserie-Style
Crystal Sapphire with AR Treatment
Movement Base Miyota 9015
Movement Type Modified Automatic
Movement Appearance Calibre 5134-Style
Day Display Yes
Date Display Yes
Week Indication Yes
Month Display Yes
Moon Phase Yes
Leap-Year Indication Yes
Automatic Winding Yes
Individual QC & Movement Testing
The specifications above describe the construction and technical configuration of the BBS 26574ST. Individual movement performance, physical measurements and calendar operation can vary between examples.
For first-hand Timegrapher results, measured dimensions, weight, movement testing and perpetual-calendar function testing, see our BBS Factory AP Royal Oak 26574ST QC Test.
FAQ
What is the full reference of the BBS Factory 26574ST?
This configuration is based on Ref. 26574ST.OO.1220ST.01.
What size is the BBS Factory AP 26574ST?
The supplied specifications list a 41mm case diameter and approximately 11.4mm thickness.
What movement does the BBS 26574ST use?
It uses a Miyota 9015-based modified automatic movement with Calibre 5134-style visual architecture.
Is the BBS movement an original AP Calibre 5134?
No. The BBS movement uses a different underlying movement architecture and should be classified as a 9015-based Calibre 5134-style movement rather than an original Audemars Piguet Calibre 5134.
What calendar information does the BBS 26574ST display?
The supplied configuration includes day, date, week, month, moon phase and leap-year indications, in addition to the conventional hour and minute display.
Where can I see actual movement and function testing?
Actual Timegrapher results, measurements and calendar-function testing can be found in the BBS Factory AP Royal Oak 26574ST QC Test.
