The central seconds hand on the dial is not an aesthetic choice: it's a technical decision that changes how the movement is constructed. In traditional manual-wind calibers — the Unitas 6498 is the most cited example — the seconds hand lives at 6 o'clock, on its own axis, because the gear train doesn't pass through the center. Moving it to the center requires additional wheels, often supplementary bridges visible from the caseback, and a kinematic path that doesn't always work without sacrificing thickness or power reserve.
In German it's called Zentralsekunde, and the word is still used today in catalogs from brands like Kallinich Claeys precisely because it signals a specific constructive choice. In English central seconds, abbreviated CS in designations like those used by Chopard in the Alpine Eagle series. The concept is identical: the hand starts from the central axis, travels the entire dial in sixty seconds, and shares the arbor with the hour and minute hands.
The distinction that really matters at the workbench is between derived central seconds and independent central seconds. In the vast majority of movements, the seconds hand is powered directly by the main train: it stops when the barrel stops, and starts again with it. Independent central seconds have instead a dedicated train, separate from the main mechanism. It's a rare solution, expensive, and technically more complex to regulate.
The regulator display inverts the visual hierarchy: minutes remain at the center on a long hand, hours are relegated to a subsidiary register — typically at 12 o'clock in Swiss tradition, at 3 o'clock in German tradition as in the Moritz Grossmann — and seconds occupy another subdial. It's not a case of central seconds, but it's the historical context from which the concept takes meaning: observatory and laboratory watches that inspired this layout were measuring instruments, not decorative objects, and minute readability was paramount.
In aviation watchmaking, the central position of seconds was linked to hacking: stopping the hand to synchronize it with a radio signal requires that hand to be visible and unambiguous. A seconds hand at 6 o'clock on a crowded dial, in the cockpit, with gloves on, is a problem. In the center, it's not.
I don't know whether the IWC caliber 61, often cited as the first IWC wristwatch movement with central seconds, actually has absolute priority in this category: the patent history of central seconds in wristwatch calibers in the 1930s and 1940s is complicated, and I don't trust absolute primogeniture claims without direct documentation.