Chronograph pushers — also called pushers, from the Anglo-Saxon terminology now firmly established in the workshop — are not all the same, and the difference is far more than aesthetic. Before design comes into play, what matters is the type of actuation and the degree of water resistance it guarantees to the case.
The fundamental distinction is between threaded pushers and pump pushers. Threaded pushers, like those on the Rolex Daytona, have a screw thread that locks them against the case: before operating the chronograph you must unscrew them, then screw them back in. In its original intent, this was a solution to improve water resistance; today, with modern gaskets, many technicians consider it redundant, but it remains a signature of the model. Pump pushers, on the other hand, are pressed directly, without preliminary operations: they are the classic solution, the one you find on three vintage chronographs out of four that pass through my workshop.
Within the category of pump pushers there are precise morphological variants. Piston-style pushers have a cylindrical, protruding profile, deliberately robust: you see them on military and sports chronographs from the 1950s and 1960s, on movements like the Valjoux 23 or caliber 11, and they directly evoke the industrial aesthetic of that era. Pump-style pushers in the strict sense, instead, have a slightly domed, softer shape, found on historical Breitling Navitimer watches, first-generation Zenith El Primero, on that whole family of chronographs where the pushbutton seems almost swollen outward. The difference between the two types, to a trained eye, is sharp; to an untrained eye, less so.
A specific variant arose for operational use: the oversized pushers on military pilot chronographs, designed to be operated with gloves. Hamilton's Type H-75 and certain titanium Hanhart watches maintain this geometry for historical consistency with the original CP-1s from the 1960s and 1970s.
At the opposite extreme are flush-mounted pushers, integrated flush with the case with no protrusion. Porsche Design introduced them with IWC in the 1970s as a choice of formal cleanliness; today you find them on certain contemporary chronographs where the designer wants to reduce the lateral profile of the case. The compromise is ergonomic: pressing a flush pushbutton is less immediate, especially with wet fingers.
Knurled pushers — cross-hatched — are a functional detail before they are decorative: the knurling increases grip and echoes the aesthetic of automotive controls, as seen on certain Chopard chronographs tied to the world of racing.
Pushers can receive surface treatments independent of the case: black DLC (Diamond-Like Carbon) is applied specifically to pushers because they are the surface most subject to friction from repeated use. A pusher pressed a hundred times a day will scratch before any other part of the case.