Frederic Piguet 21 (broken balance staff)

Runs but has broken balance staff.
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Frederic Piguet 21

Features
manual wind

Data:
9''', Dm= 20.4mm, Do= 20.8mm
H= 1.75mm or 1.73mm
F= 0.3mm
T= 0.8mm
17 or 18 jewels
f = 18000 A/h or 21600 A/h
power reserve 42h

Balance staff U3304
Stem W3255
Hands
1.00 x 0.5mm