Review: Angelus U51 Diver Tourbillon

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The curious genre of saturation diving watches with a tourbillon is one which is quite unusual. But from the quirky stable of Angelus comes not one, but two such monikers – the U50 Diver Tourbillon and the U51 Diver Tourbillon. Neither are new, being variations of older, now sold out versions. Both are value buys for a watch equipped with a tourbillon. We take a close look at the U51 Diver Tourbillon.

Angelus U51 Diver Tourbillon

Some have called a diver tourbillon an oddity designed to bring the nerd out of us watch collectors. And strangely, it does resonate with me. The concept of an iron fist in a velvet glove comes to mine – the tourbillon, perhaps a fragile and somewhat finicky contraption in a watch which is built to be robust, and where one relies on for one’s own safety. The juxtaposition is intriguing.

A veritable study of contrasts. And one which we can safely attribute to the immense ingenuity of one Sebastian Chaulmontet, who designed the movement. Sebastian was then with La Joux Perret, who belongs to the same owners as Arnold & Son and Angelus. All three companies are part of the Citizen Group.

The case, dial and hands

The case on the U51 is titanium and measures a rather massive 45mm in diameter with a height of 15.47mm. The case is very sturdy and is rated for saturation diving up to 300m. Two crowns adorn the side – one is used for the inner rotating dive bezel, and the other to operate the movement – time setting and winding. At 9 is an automatic helium escape valve, enabling the watch to be used for saturation diving.

The inner bezel feels good with positive assurance of each click. The bezel is rather attractive with orange and blue sections in the typical diver watch arrangement, and marked with the minutes in 5 minute intervals by numerals.

The Angelus logo is printed on the underside of the sapphire glass, and appears to float over the dial.

The dial is skeletonized and laid out such that the tourbillon is placed between 6 and 7, somewhat skewed to one side, perhaps as a consequence of the main crown which is placed between 3 and 4. As a result, the dial looks asymmetrical and rather opposed to the design principles used for sister brand Arnold & Son.

The skeletonitisation of the dial means that there is hardly any dial left on the face side of the watch. What remains is a circular ring inwards of the dive bezel which is marked with large luminous squares for each hour and ruled for the minutes.

Though we wouldn’t characterise legibility as excellent, it is not compromised too much. Especially given that it is a skeleton dial, and the rather complicated looking plates are visible. The movement plates visible from the dial side is in a rather a monotonal grey, and the hands are large, and filled with lume, which helps. The minute hand carries an orange identifier and is longer than the hour hand and both are box shaped. The subsidiary seconds hand is also marked in orange, but is less visible due to its small size, but for a dive watch the seconds are not a critical legibility requirement.

The movement: Angelus Caliber A310

The movement is the Angelus Caliber A310, which we believe to be a variant of the A300 previously seen on the Angelus U50 Diver Tourbillon. The dimensions of both calibers are identical, as is the bridge layout. The main difference is that the movement on the A310 is constructed from titanium plates and bridges, while the A300 is standard rhodium plated brass. As a result, the movement makes the watch (also in titanium case) feel very light. Also the A310 has a power reserve of 120 hours instead of the standard 60 hours on the A300. Angelus credits this to the silicon escapement

The tourbillon itself runs on ball bearings for improved efficiency, and beats at 28,800 bph.

Bridge layout as visible from both sides of the watch looks like a complex web, which is not unattractive. From the dial side, the tourbillon’s position between 6 and 7 is unusual, as noted, and the cage mirror finished with chamfered and polished edges.

The bridges are sand blasted and retain the natural titanium dark grey hue. On the dial side provide a good backdrop with high contrast to the hands to make legibility quite good. From the back, the bridges are pierced with rounded rectangles, making it look rather industrial. The finish is an excellent engineering finish, with good attention paid to the screws, chamfers and countersinks.

The competitive landscape

The competitive landscape for a saturation diver with tourbillon is very small. Coupled with the limited edition of only 25 pieces and a very reasonable price of CHF 32,800, it is hard to find a worthy opponent.

Roger Dubuis used to do one called the Easy Diver Tourbillon (used prices at Chrono24 indicate current price to be about CHF 88k) which is rated to 300m depth, but not equipped with a helium escape valve, so saturation diving duties may be lacking.

The Richard Mille RM25 (introduced in 2015, and now sold out. RRP was US$750,000 for the ti case version) is a possibility, but it too lacks a helium escape valve. The RM25 is more complicated in that it is also a chronograph.

So perhaps rivalry is best expressed in the U51’s sibling – the Angelus Diver Tourbillon U50. The U50 sports the A300 movement, which is the base for the A310. The plates are brass, and the latest version, shown below is the Black Edition, has the plates with black ADLC coating. It matches the U51 almost exactly, with a black ADLC titanium case. The colour scheme is monotone grey on the entire watch. Retail is CHF 30,750.

The sibling – Angelus U50 Diver’s Tourbillon Black Edition.

Concluding thoughts

As mentioned, this is one watch which is a study in contrasts. The strong and robust but yet complex and delicate. We have not only a tourbillon, but one which flying one by design, with the lack of an upper bridge, might be seen as even more fragile. Up the ante even more with the case designed for saturation diving, with an automatic helium escape valve. All the contrarian values of tool watch design seem to be at odds. But yet it works. The Angelus U51 is quite an attractive watch. The use of colour for the dial ring brings a level of liveliness. The wave like bezel carries a character, amplified by the skeleton dial which allow a good look into the movement. And that tourbillon. Quite a magnificent beast. Plus, least of all, the pricing is very reasonable for a tourbillon watch.

On the wrist, the 45mm case sits well. And the entire watch being in titanium feels very light.

The U51 sits nicely on the wrist, feels extremely light, thanks to the titanium case and movement. And is comfortable for all duties, be it for a dive, or in a suit for the board room.

Photo Notes: Photographed in-situ with the Leica SL Type 601 with Leica TL APO-Macro-Elmarit 60mm f/2.8 ASPH. Lighting by Profoto Compact 600 as main light and Canon EX580II as rim light.

Angelus U51 Diver Tourbillon Technical Specifications

Functions Hours, minutes, small seconds, unidirectional rotatable 60-minute indicator
Calibre A-310, mechanical hand-wound, one-minute flying tourbillon
Jewels 23
Diameter 32.80 mm
Height 4.30 mm
Power reserve 120 hours (5 days)
Frequency 4 Hz / 28,800 vph
Lever escapement Silicon
Decoration Sandblasted plates and bridges, wheels with Angelus six-spoke design, tourbillon cage with chamfered and polished edges
Dial Openwork with blue and orange chapter ring. Hours’ indexes, chapter ring’s Arabic numbers and hands filled with Super-Luminova
Material Grade 5 titanium. Sandblasted, brushed or polished finishing
Diameter 45.00 mm
Thickness 12.47 mm
Crowns Screwed and engraved with Angelus logo
Crystal Box shaped sapphire with anti-reflection coating both sides
Back Sapphire
Water resistance 300 m / 1,000 ft
Material Blue rubber embossed with Angelus logo
Buckle Folding, grade 5 titanium
Limited edition 25 pieces
Reference 0TDCT.E01A.K008D
World retail price CHF 32’800 without taxes (prices can be subject to change)


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