Rare Omega prototype ref. 055 ST 175.0035, steel case, gold Roman numerals, vintage charm. Never commercialized, rich heritage ties. | Omega

A unique Omega prototype

This Omega ref. 055 ST 175.0035, a self-winding bissextile perpetual calendar with moon phases, is a prototype and unique piece, never commercialized.

It was one of the personal timepieces of Anton Bally (1946-2002), former director of ETA S.A., one of the companies in today’s Swatch Group.

credit: goldor.ch

The steel case measures 35.1 x 10.3 mm.

Some consider that it can be compared with the ‘Speedmaster Reduced’ collection...

... while the 1116 caliber and the dial are related to the ‘Classic Heritage’ line and the ‘Louis Brandt’ perpetual calendar, ref. 175.0300.

The white dial features yellow gold applied radiating Roman numerals (II-IV-VI-VIII-X-XII) and indexes.

The crown is hexagonal and signed.

The solid caseback is stamped in the centre with the logo and name ‘Omega’, and the mention ‘House founded in 1848’.

credit: FutureGrail, Atelier Victor (Speedmaster Reduced) & Pushers.io (Louis Brandt Perpetual Calendar)

Does this unique piece appeal to you?

I personally find it very nice from an aesthetic standpoint.

Thanks for looking.

Best, Emmanuel

💰362 Marketplace Listings for Omega›

The nearly total absence of perpetual calendars from Omega's line-up . . .

By: Dr No : May 8th, 2026-22:30

. . . is puzzling as they've made day-dates, triple calendars, and moon phases for a century. I was aware of the Louis Brandt model of the '90s (and saw it in the metal at OmegaMania), but had no inkling of this prototype. Are you positive regarding the d...

The AP 5548 which is quite similar to this watch is 36mm. 35mm seems plausible.

By: jmousey : May 8th, 2026-23:19

Indeed and the Louis Brandt PC is only 34 mm.

By: quattro : May 9th, 2026-06:59

I have added a few links in my reply to Art above. Best, Emmanuel

These are indeed the dimensions mentioned by FutureGrail.

By: quattro : May 9th, 2026-06:58

Check here: https://www.futuregrail.com/auctions/Omega/Ref-055-ST-1750035-prototype-unique-piece-former-property-of-Anton-Bally-director-of-ETA-SA-stainless-steel/May2025/5 And it seems consistent, as the Louis Brandt PC is only 34 mm: https://pushers.io/...

My recollection of the Louis Brandt perpetual is apparently like my recollection . . .

By: Dr No : May 9th, 2026-20:55

. . . of high school years: larger than life. 😄

😅 I've just posted a thread dedicated to the Louis Brandt PC:

By: quattro : May 9th, 2026-22:35

I love the second gen pieces.

A watch that widens the eyes as you get closer and closer!

By: KCLQMULKU : May 8th, 2026-23:09

What a beauty, and such unique history!

Yes, I also find it to be a very nice piece.

By: quattro : May 9th, 2026-07:00

Best, Emmanuel

I like it👍

By: Vetnov : May 9th, 2026-01:58

Wonder why it wasn’t a commercial model.

I have no clue, unfortunately.

By: quattro : May 9th, 2026-07:00

Best, Emmanuel

The type needs a bit of tweaking but it's nice...

By: mdg : May 9th, 2026-04:10

Yes, but nothing major, imo.

By: quattro : May 9th, 2026-07:02

Best, Emmanuel

While this is a piece unit, what really appeals about Omega is that they often bring these kinds of pieces that might not fit into a strict product plan but surprise and delight exactly because of that 👌🏻👍🏻

I completely agree.

By: quattro : May 9th, 2026-07:03

But still regret that such a timepiece never became a regular production model. Best, Emmanuel

Absolutely agree with you - I would be sorely tempted 👌🏻🤞🏻

By: KMII : May 9th, 2026-07:06

It makes me want to see the Louis Brandt in person someday.

By: quattro : May 9th, 2026-07:25

There's something special about a compact . . .

By: Dr No : May 12th, 2026-18:24

. . . perpetual calendar. Had I been aware of its dimensions, I might well have chased down a Louis Brandt perpetual when perpetual calendars were my passion.