From Horology magazine, November, 1937
So many watches come in for cleaning only and after they are cleaned nicely and put back together some of the watches balk or stop running in the course of a few hours or maybe during the night. Seemingly no cause that can be found, jewels are all perfect, and no side play.
Find the greater trouble in Swiss watches as well as some American watches. We found the trouble in most all makes of watches.
Answer: From your letter we conclude that your troubles are not due to just one fault. There are hundreds of reasons why a watch will stop. Only an examination of each individual case will determine the exact cause.
Our suggestion would be an intensive study of both theoretical and practical horology. With greater knowledge of the subject you will find increasing ability to recognize defects in watches. As far as we can see the only solution to your problem is further study.