Keystone Chrono Works - absolutely five star service in every way. I have personally sent 5 or six watches for repair, adjustment, and modification. They also built two cusom watches for me out of parts that I sourced from around the world.
The lab/shop is complete with the latest watchmaking equipment and tools. They also have an excellent parts supply which means your watch gets fixed with only the best available OEM (or custom) parts.
A nice touch - as your watch is opened, pictures are taken through the microscope so you can see failed parts, dirty movements, scratched crystals . . . etc., etc., nothing but top quality service here !
It seems as though there is no job too big, or small for Keystone Chrono Works, and I highly recommend - 5 stars.