Do you have and use a beater watch that you honestly don't care what happens to it? A watch that you would wear while working on machinery or in a way that would almost guarantee that the crystal would be scratched? My sense is that "beater" has come to mean a beloved lower-priced watch, not a watch that you really don't care about damaging. Even when a "beater" is beaten up, you don't want it any more beaten up.
I contemplate this question as I prepare to paint my back fence today.
I think a true beater would have to be a $20 chartreuse woman's watch or something like that for me to truly not care about it.