Piston pushers are chronograph buttons with a plain cylindrical form that sticks straight out from the side of the case. They are the classic pusher type. They were in use by the 1930s, and most watchmakers still use them.
Why are they called piston pushers?
They look like small mechanical pistons. Press one and it slides into the case, then slides back out. This movement and the plain round shape set them apart from rectangular, oval or integrated pushers. The head is wider than the stem, so the finger has a decent area to press on. Piston pusher and pump pusher are often treated as two names for essentially the same button. Mushroom pushers are a flattened variant of the pump pusher.
Does the pusher shape tell you about the movement?
No. The outside shape of the pusher says nothing about the chronograph mechanism inside. A watch with piston pushers may use a column wheel, a cam or another system to control the chronograph. The buttons alone do not show which one is fitted. Well-known chronographs with pump pushers include the Zenith El Primero and the Omega Speedmaster.
How do they differ from screw-down pushers?
A pump pusher starts the chronograph with a simple press. A screw-down pusher has to be unscrewed first. Some makers fit screw-down versions of piston pushers. On these, protective collars have to be unscrewed before the chronograph can be used. The Rolex Daytona shows both types. References 6239, 6241, 6262 and 6264 have pump pushers, the standard button-style controls at 2 and 4 o’clock. Other Daytonas use screw-down pushers that can be locked with a rotating barrel-shaped collar.
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