I have seen similar marks on various watch parts in the past, some of which suggest that a watchmaker has cleaned parts from several different watches in the same basket at the same time and has marked the parts to show which parts belong to which watch. Either many of the parts from the same watch that I have been working on have the same mark (1, 2, or 3 lines, or a v) or the calibre has been scratched onto a part. I have even seen the marks duplicated on the case.
It is just speculation on my part that this is the rationale behind these marks, and if I'm correct then it has to be acknowleged as being a pretty poor practise if not out and out vandalism, but the marks always seem to me to have been made as part of a service procedure, they don't look like they were marked up during manufacture or assembly.