In watchmaking, the word quality doesn't have a single meaning: it depends on what you measure and who certifies it. From the bench, I've learned to distinguish three levels of assessment — functional precision, aesthetic finishing, and constructive solidity — because a watch can excel in one and disappoint in the other two.
On the precision front, the most well-known reference remains COSC certification, which imposes a tolerance of −4/+6 seconds per day on each individually tested caliber. But alternative standards exist, and in some cases, more stringent ones. The Master Chronometer by METAS — adopted by Tudor among others — guarantees 0/+5 seconds per day with resistance to magnetic fields superior to 15,000 gauss. The Qualité Fleurier, which concerns Chopard L.U.C movements, is perhaps the most rigorous protocol in the industry because it verifies the movement mounted in the case and subjects it to simulated wear cycles. The Minerva Laboratory Test 500H certification instead indicates extended testing — probably 500 hours — developed internally by the manufacture for caliber M13.26.
On the finishing front, the Poinçon de Genève — also called the Hallmark of Geneva — is the mark that certifies construction, assembly, and finishing according to Canton of Geneva regulations. Having a good caliber isn't enough: the movement must be physically made in Geneva and respect precise criteria on every visible component. Roger Dubuis applies it systematically to all production; Vacheron Constantin carries it on Overseas models as well. Finding it on a steel watch is still relatively rare.
Among mid-tier certifications, Sellita's Élaboré grade sits between Standard and Top Grade. It involves regulation in three positions, average tolerance of ±5 seconds per day, and visible finishing such as Côtes de Genève, perlage, blued screws, and fluted jewels. La Joux-Perret's Soignée grade, instead, represents the highest level of the manufacture, with manual work on bridges and rotor.
Some manufactures adopt proprietary protocols without external marks. Armin Strom, for example, assembles each movement twice: complete assembly, inspection, disassembly, verification of every component, and final reassembly. It's a costly approach in terms of time, but it almost completely eliminates post-assembly regulation drift.
In minute repeaters, quality is heard as well as seen: Patek Philippe judges the harmony between the strike of the hours, quarters, and minutes, the duration of sound, and the depth of the gong. These are parameters that don't appear in any written certification but distinguish a successful piece from a merely correct one. In some ways, it's the most honest form of quality control I know.