I will be pleased to be proven wrong, but my experience suggests (at least from the photognaph) that bringing back the hairspring to its original confitions is probably wishful thinking.
Unfortunately most collectors do not pay attention to the condition of the movement hoping that a qualified service will be able to fix everything. However, this is not the case. Most watches can be made running in an apparently reasonable way, but this is far from the running conditions they originally were up to.
A watch which loses 20 seconds when worn and gains 20 seconds overnight will give the impression to run very precisely but, in reality, it doesn't.
Most 105.003 show a nearly definitive version of the 321 caliber (the latest starting from about serial 24,5 mil) and, differently, from the previous versions (the CK2915-105.002 range), with some tinking can be made nearly chronometer grade.
But the movement must be very well preserved and not only from the cosmetic point.
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