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Old 13 July 2023, 01:54 PM   #9
wm82
"TRF" Member
 
Join Date: Sep 2012
Location: sweden
Posts: 155
The 4130 since 2019 sometime, uses the same balance as the 9001 skydweller. It has a different shaped overcoil, and under the 4130 balance bridge the coils can get tangled if the movement received a sudden shock.
Its an easy fix for an on site watchmaker. Rolex has come out with a "hotfix" for those affected hairsprings and since changed the shape of the curve a bit.
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