This is an accidental mistake of the person applying pressure on the screw driver.
As he/she completed the process of tightening, he/she withdrew the screw driver slightly too fast, while pressure was still turning the tool, hence you see the slight uneven edging at the end of the gold screw.
This happens also because the gold is soft. Also, the screw driver must be withdrawn vertically, a slight off angle, say 80 degrees instead of 90 to the plain, and argh.
Most customers will miss this accident/flaw. Even a loupe will not reveal this error, which can be seen only if both screw and lens is held perfectly motionless.
Which is one reason why I photograph my watches with still white lamps from 3 directions on 3 different planes.
I do not usually do this, unless the watch is very costly.