What does this gear wheel do ?

[familyguy]

I've often seen photos of the rear of movements with a gear sitting on top that does not appear to mesh with anything, does it serve a purpose ?

[wls1971]

Its the centre seconds drive wheel attached to a extended pivot on the third wheel in the case of this movement the seconds hand pinion should be in the centre of the movement and held in place with a spring. On this movement that has been broken and only the end is seen attached by a screw on the barrel bridge and the second hand and pinion are missing

Edited November 6, 2017 by wls1971

[oldhippy]

5 hours ago, wls1971 said:

Its the centre seconds drive wheel attached to a extended pivot on the third wheel in the case of this movement the seconds hand pinion should be in the centre of the movement and held in place with a spring. On this movement that has been broken and only the end is seen attached by a screw on the barrel bridge and the second hand and pinion are missing

Spot on.

[familyguy]

Thanks for that I can now see the bit of broken spring and the hole where pinion shaft would have passed through.