Mercury Altmann × Isotope

Osaka Cloisonné Enamel

For many years I wanted to create a watch inspired by the remarkable artistry of Japanese manhole covers. These objects belong to everyday urban life, yet they often display an extraordinary level of graphic sophistication, cultural symbolism, and civic pride. For a long time, however, I could not find the right way to approach the idea.

In December 2024 I came across Björn Altmann’s book Manhole Covers of the World, and it became clear that I was not alone in recognising the artistic value of these designs. The book documents their typography, composition, and visual language with the same respect normally reserved for more conventional forms of art.

After a short conversation with Björn, we realised there was a natural way to bring two artistic expressions together: his book and a very small series of watches.

This collaboration resulted in something entirely new at this level of craftsmanship. The dials are made using grand feu cloisonné enamel on sterling silver bases. Fine silver wires form the structure of the design while multiple layers of vitreous enamel are applied and fired individually. Each colour requires its own application and firing stage before the dial can be hand-finished.

Because of the complexity of the pattern and the number of firing cycles required, completing the five dials took almost a full year.

The manhole cover depicted originates from Osaka and features Osaka Castle at its centre, framed by flowing water and cherry blossoms in bloom. The surrounding motifs symbolise the city’s history, seasonal renewal, and its relationship with water.

The Japanese characters cast into the original cover read 大阪市 (Ōsaka-shi), meaning Osaka City. This identifies it as an official municipal design rather than a decorative reinterpretation. This connection to real urban infrastructure is precisely what makes these objects so compelling. They are functional, civic, and quietly artistic.

Translating this manhole cover into a watch dial was not about simplification but about fidelity. Every line, colour, and proportion was carefully adapted to preserve the spirit of the original design while reinterpreting it through traditional watchmaking techniques.

Only five dials were produced.

Each watch includes a copy of Manhole Covers of the World, signed by Björn Altmann.

— José Miranda

Co-founder, Isotope Watches

About Björn Altmann

Björn Altmann is an independent designer, illustrator, and typographer with more than 17 years of experience in the creative industry. With a strong focus on branding and a longstanding interest in watches, he has contributed to the watch industry as an illustrator, dial designer, and type specialist.

Based in London for many years, he worked both within agencies and independently, collaborating with major international brands.

He has built a strong reputation within the watch world through collaborations with established brands, independent makers, and private collectors, contributing across illustration, dial design, typography, and special commissions.

His work extends to major editorial and publishing projects, including the illustration of more than 500 watch references for a landmark publication, and has appeared in industry publications, auction projects, and collector-focused platforms.

Björn is the author of Manhole Covers of the World, published by the Swiss publisher niggli.

Cloisonné Enamel Dial Production

Because of the complexity of the pattern, and in order to keep the project commercially viable, we spent nearly twelve months developing a production method that would allow us to create just five dials.

To control costs while preserving depth and definition, the solid silver dial base is first CNC-machined to create recessed areas. Fine silver wires are then applied by hand on top of this engraved base to form the cloisonné structure.

Production steps

1. CNC engraving

The solid silver dial base is engraved to create recessed sections.

2. Hand-applied silver wires

Fine silver wires are shaped and positioned by hand to create the cloisonné cells.

3. Enamel filling

Vitreous enamel powder is placed into the spaces between the wires.

4. Kiln firing at 850°C

The dial is fired in a kiln at approximately 850°C. The enamel melts, bonds to the silver base, and cools naturally.

After the first firing the enamel shrinks, leaving the surface uneven. Additional enamel is applied and the dial is fired again.

This filling and firing cycle is repeated roughly ten times until the dial reaches the correct thickness.

5. Polishing and inspection

The dial is polished to create a smooth surface. If air bubbles or micro-holes appear, the dial must return to the kiln for further enamel application and firing.

Each dial requires many firing cycles, extensive handwork, and strict quality control before approval.

In the end, only five dials were completed.

The Altmann × Isotope cloisonné edition is now ready to ship.

Each watch owner will also receive a signed copy of Manhole Covers of the World.

Technical Specifications: