iW Magazine
Featured News

Paul Gerber’s Migrating Moon

Master watchmaker PAUL GERBER makes it simple to add a lunar dimension to any watch.

Whether mechanical or electronic, modern watches can house myriad complications and displays- both traditional and tech-driven. In many cases these added values create an air of complexity that gadget-geeks love to show off even if these functions are rarely (if ever) utilized. On the other side of the coin are purists who appreciate a clean façade and the elegance of a ‘less is more’ dial.

If your own taste for watch-wear lies in the more sober dials, but you still appreciate a bit of watchmaking savvy on your wrist, master watchmaker Paul Gerber has now made it simple to add a lunar dimension to that simply exquisite Jaeger-LeCoultre Geophysic or that purely elegant Zenith Elite.

Paul Gerber

Early in 2017 one of my long-time watch friends/clients insisted that I must put an evening aside to meet with Paul Gerber. Already a fan of Herr Gerber’s watches (double rotor, triple rotor, three-dimensional moon phase) and trusting my man Moritz would not demand my time without good cause, I was more than willing to invest an evening in Zurich to discover what Gerber was up to. It was here while we all enjoyed the fruits of the Reinheitsgebot that Paul introduced me to his new device; a small moon phase sans timekeeper.


Designed to be mounted directly into the strap rather than the dial, this lunar display came as a complete surprise. Expecting one or another complication, or possibly a new super-accurate mechanical escapement, I was taken completely aback. Not least of my surprise was the fact that Gerber was fabricating a device with a quartz controller.

My initial impression was that of surprise. Since my own pre-conceived notions had prejudiced my expectations, it took a moment to adjust to something completely out of left field, like that first sip of a fine whiskey. I soon came to savor the flavor of the concept and the EPR 52 mini-moon phase.

Too small for any kind of mechanical motivation, Gerber’s new strap-mounted moon phase (EPR 52) may be battery operated and quartz controlled, but within a 12mm x 5.35mm capsule Gerber has integrated no less than 54 parts in the moon-phase movement (excluding electronic parts) along with another seven machined parts for the capsule enclosure to create a truly unique watch collector’s accessory.

I asked Mr. Gerber to explain how he devised the Micro Moon Phase and what a collector can expect if he or she purchases one.

How many parts did you need to make the moonphase?
I only counted the mechanical parts! The movement consists of 54 parts and the enclosure out of 7 parts. The total of mechanical parts is 61, again – not including any of the electronic parts.

When did you start working on this?
I first thought about the idea in December of 2016 and had the first prototype finished in February 2017.

How long will the battery last - and is it a standard and easy to replace style?
The battery will last three years and is a conventional micro cell, Renata 335, SR512SW; diameter 5.80mm, height 1.25mm.

How many variations of the straps available?
At this time I have five leather and one natural rubber strap. In the future, I’m sure I will be adding and offering additional leather straps. However, the selection will be limited as the strap will have to be at least 20mm to 22mm wide and 4.0mm to 4.5mm thick.

Can it be retrofitted into an existing strap?
The Micro Moon phase can be retrofitted to an existing strap if the strap meets the measurements mentioned above. There is an additional charge to do the retrofit.

Do you plan to find a way to integrate into a metal bracelet?
For sure that is an option, however, it is even more difficult in terms of the measurement restrictions mentioned above since a steel bracelet is not typically 4mm thick. What will be an option for sure is a gold enclosure, price upon inquiry.

How much does it cost?
The moon phase with titanium enclosure will be $995 without the strap. Our leather straps start as low as $80 and go up from there. The caoutchouc (natural leather) strap is $90 including installation.

Is there any lume?
Right now I only have the 18-karat gold moon without Luminova. Different versions are planned, but it is too soon to talk about them.

How accurate is the moonphase?
I calculated the gear ratio in a conventional manner with a one-day variation over a three-year period. After three years the battery will have to be replaced in any case. Re-adjusting the movement while replacing the battery will eliminate the one-day error.

What was your biggest challenge to create this?
The biggest challenge was size as it needs to fit inside the strap. You can imagine the whole device can fit on a fingertip, any bigger it would not look right. Yes, size was definitely the main challenge as it was difficult to achieve the objective of a three-year operation time – all integrated into the thickness of a fine leather strap.

I know the moonphase is battery powered, but can you explain how the electric power is being converted into the kinetic motion to move the disc?
The moonphase is obviously battery powered. A crystal-controlled oscillator producing only a few pulses every hour controls a step-motor which powers several gears with the correct ratio to turn the moon phase disc once in 59 days. I’m utilizing a Swiss movement, which offers extremely small electronics, which together with my moon phase mechanical movement are so small as to fit in this capsule.

Are these available now and how long for delivery?
They are ready with a delivery time of one month.

Any warranty included?
I offer a two-year warranty.

Any specifics that you might like to add?
This project entailed several obstacles. There were no sapphire crystals available in this small size, so I had to have them manufactured to my own specifications; the same with O-rings to make it watertight to 3 atm. They were also difficult to find.

Where can collectors buy them?
In North America collectors can buy directly from Moritz Elsaesser at Mainly Watches via www.swisswatchmakerharvardsq.com or you can call to learn more at 508-429-3004. Collectors outside North America can contact Gerber directly via www.gerber-uhren.ch

iW InsideriW Insider brings you news and new watches from new and well-known brands each week.
Sign up now to keep “watching.”
There was a problem. Please try again.
Thank you!