Perpetual Calendar
August 3, 2026
The Roysdon Model 3 - Perpetual Calendar prototype. This watch evolved over the years with many iterations to the perpetual calendar mechanism (a 3:1 scale model example is shown in the photos). In all, 100 additional parts were added to the Model One movement to accommodate the perpetual calendar.
The case has a display back to highlight the hand finishing (chamfering or "angelage") on the bridges and 18k gold wheels, graining and "pearlage" on the mainplate, and flame-blued screws.
The dial has 7 different guilloche patterns that took 11 different setups. It also has 18k gold chapter rings, indices, and hands with pad printing done on the in-house designed and built pad printer.
The Model 3 dial includes the following time and calendar elements:
- center dial: basic time in hours and minutes,
- right subdial: month and date (all prime numbers, an "Easter egg" for the mathematicians out there),
- bottom subdial: seconds and moon phase,
- left subdial: day of week and day/night indicator,
- top subdial = year/leap year.
This was a few years in the making. We hope that you appreciate it as much as we do.
Special note: All components of Dr. Roysdon's timepieces (case, band, dial, movement) are built entirely in-house by him, with the exception of the ruby jewels, sapphire crystals, hairspring and mainspring.
Perpetual Calendar Dial
July 20, 2026
The new Model 3 dial is a hand guilloched silver with 7 patterns, 18k gold angular chapter rings with pad printed markers, and 18k gold hands and hour indices.
This was a very challenging project. The hand guilloche took nearly a week to perfect on a single monolithic dial, then whiten (depletion gilding) to a matte white. The most challenging aspect is the combination of straightline and rose engine guilloche with separations of only 0.5 mm. This requires extreme precision and care when advancing the cutter through the material and stopping at exactly the correct spot so that the adjoining guilloche is not touched.
The chapter rings were machined, circular grained on a lathe, and then pad printed on our custom built pad printer. This also required making a new cliche for the pad printer. The chapter rings are angular (not flat), meaning that the inside diameter has a height of 0.25 mm whereas the outside diameter has a height of 0.4 mm. This improves the reflection in the light and creates a more dramatic 3D appearance to the dial.
The hands and indices were milled in 18k gold and then hand shaped and polished.
Finally, everything was assembled and the result is striking.
Perpetual Calendar
January 13, 2023
Dr. Roysdon really enjoys performing “studies” of complex problems. The perpetual calendar is a great example of complexity, with 78 components that sit atop a standard mechanical watch movement, e.g., the Model One movement. Based on the 1920’s Dubios Depraz design, this study was performed at 2x scale to evaluate each rotational part and their influence on the progression of months of different lengths, as well as the critical leap year month of February (as shown in the bottom video). This prototype was designed in Fusion360 and machined on the NS CNC Elara 4-axis Mill and Boley F1 Lathe. The scaled down prototype will soon be in the Roysdon Model 3.
Micro-endmills are required for this work; 0.1 mm, 0.5 mm and 1.0 mm (see photo).
This perpetual calendar includes the following complications:
day/night indicator
moon phase
day
date
month
week number
year
leap-year indicator
There are 4 corrector levers to properly align the various complications; see the bottom video.
