This is generally considered damaging the customer's watch these days. There's no reason why any marks need to be made inside a case...there are other ways of tracking if you have serviced a particular watch or not.
Would you consider a watchmaker scratching a series of numbers into the movement plates/bridges just part of the history of the watch too? Many "old school" watchmakers still do this kind of thing to keep track of parts. My view is you need to change your process if you can't keep track of what part goes in what watch without scratching the hell out of them...
Click to expand...