If you’ve never heard of a “deadbeat seconds” complication, that’s likely because it has been antiquated since Seiko introduced the quartz movement in 1969.
But like so many aspects of watch culture, just because it doesn’t need to exist, doesn’t mean there isn’t a market for it. Ironically, the complication, which causes a mechanical watch to beat once a second like the simplest quartz movements, requires an impressive feat of horological engineers.