A one-watch collection works when the watch suits most of your life without making its compromises irritating. It does not need every complication, the highest depth rating or a design that disappears into every outfit. It needs to do the jobs you actually ask of it, in a case you enjoy wearing.
The Sinn 556 I RS, Longines Conquest 38 and Oris Aquis Date 41.5 offer three sensible starting points. Each is an automatic with a date, but they differ in appearance, reserve, water rating and bracelet design. Choosing among them begins with deciding how prominent a role the watch should play.
Sinn 556 I RS: keep the dial direct
The Sinn uses a glossy black dial with pale indices and a red seconds hand. Its 38.5 mm steel case is 11 mm thick, with sapphire at the front and back. The current technical sheet specifies an automatic SW200-1, stopping seconds, a screw-down crown and 20-bar water resistance. The date is present without a large external timing scale surrounding the face.
Helmut Sinn founded the company in 1961, and the manufacturer connects the 556’s display with its pilot and navigation cockpit clocks. That background explains the instrument-like restraint. It suits someone who wants a watch with a clear identity but relatively little ornament, and who is comfortable with conventional mechanical ownership.
Longines Conquest 38: a more polished everyday balance
The blue L3.720.4.92.6 uses a 38 mm steel case and bracelet, a sunray dial and a date display. Its automatic movement has a silicon balance spring and a reserve of up to 72 hours. The 10-bar rating and screw-in crown support an everyday sporting brief, while the plain bezel keeps the appearance less specialised than a diver.
Longines registered the Conquest name in 1954. The contemporary collection develops that long-running identity rather than copying the appearance of the first watches. The 38 mm option makes sense if you want a relatively compact round watch that can move between work and casual clothing. Its official UK price was £2,000 at the check.
Oris Aquis Date: make the diver format your everyday format
The green 01 733 7787 4157-07 8 22 04PEB is the 41.5 mm Aquis reference discussed here. It has a ceramic minutes-scale bezel, a steel bracelet and 300 m water resistance. The current 733-1 automatic has a 41-hour reserve, so a long weekend away from the wrist can mean restarting and resetting it.
Oris substantially revised the Aquis in 2024, refining details including the silhouette, crown protection and bracelet links. This is modern development history rather than a claim that the watch reproduces a vintage original. The diver’s broader case and integrated-looking bracelet should be the appearance you prefer for ordinary days, not equipment you tolerate for a rare holiday swim.
| Watch and reference | Core dimensions | Daily-use distinction |
|---|---|---|
| Sinn 556 I RS | 38.5 mm × 11 mm | Clear indices; date; 20 bar |
| Longines L3.720.4.92.6 | 38 mm diameter | Sunray blue dial; up to 72 hours; 10 bar |
| Oris 01 733 7787 4157-07 8 22 04PEB | 41.5 mm diameter | Timing bezel; 41-hour reserve; 300 m |
Write down the non-negotiable jobs
If you check the date frequently, all three meet that need. If you want to time short everyday intervals with a bezel, the Oris supplies that function. If the watch spends several days unworn, the Longines’s stated reserve is a practical advantage over the Oris here. None of them automatically changes time zones or supplies an alarm.
Water use also needs an exact plan. Follow the maker’s instructions for the complete watch and strap, and keep water resistance checked as appropriate. A rating describes intended performance under defined conditions, while the condition of a particular watch determines whether it remains ready for that use.
Leave room for maintenance
One watch still needs servicing. Decide whether you have another way to tell the time while it is away and whether you are happy to leave it off for activities that do not suit a mechanical wristwatch. A one-watch collection is a preference about ownership, not a requirement to wear the same object through every possible situation.
Choose the Sinn for visual restraint, the Longines for a compact polished everyday balance, or the Oris if a modern diver is the design you would happily wear most often. The right answer is the watch whose compromises you can describe clearly and accept without spending the next year looking for a second watch to correct them.
Based on manufacturer information. Specifications and sources checked on 8 September 2026.
Sources: Sinn 556 I RS current product sheet, August 2026; Sinn history and ownership guidance in the 856/857 manual; Longines Conquest 38mm specifications; Conquest’s 1954 origins; Longines’ 2024 Conquest expansion; Oris Aquis exact-reference specifications; Oris on the Aquis redesign; Oris 2024 design history and clasp distinctions.
Image: AI-generated editorial illustration of the Longines Conquest 38, L3.720.4.92.6. Fine details may differ from the production watch.
