Vintage Rotary watches are of a higher quality than their modern counterparts and can be quite collectable. See the Aquaplunge service process here.
Rolex Prince Service and Repair: Calibre 7040
Zenith Chronograph Service: Calibre 146D
Gallet Chronograph - Venus 150 Service
Timing Washers - Large Adjustments to Watch Timekeeping
Sometimes the timekeeping of a watch will be very wrong even after a service - several minutes a day. If a watch is gaining a large amount of time, there is a solution - ‘Timing Washers’. These are minuscule and precisely manufactured amounts of material, designed to be added in pairs to timing screws of particular sizes of balances to affect the rate a known amount (usually 1, 2 or 3 minutes per day).