This is something I see way too often. It was common in days gone by for manufacturers to include a small semi-circular hole in the barrel lid for one to observe the mainspring and make sure that it was catching on the barrel wall (or sliding in automatics). You can properly gauge both of these situations without any visual clues. A local watchmaker apparently doesn’t know that because this isn’t the first time I’ve come across a “custom” hole filed into the barrel lid. I don’t know of many (if any) modern watches which have a hole in the barrel lid.
While this doesn’t really cause problems in barrel lids which fit to the inside of the barrel drum; in a watch where the barrel lid fits on the outside of the drum this can be a serious problem. There needs to be tension to hold the lid in place and when you place a hole in the rim that tension is gone. In this case the lid raised up off the barrel drum just enough to start rubbing and cause problems in the watch.
The worst part is the watch was in really good condition so I didn’t foresee having to replace a $48 barrel when I estimated the charges for this repair. Thank you kind “watchmaker” who single-handedly introduced a $48 error in this watch for the next guy to clean up. If you read this feel free to send me a check.