I got some very nice natural looking aging by shaking a watch case in a jar of hardened drywall screws. Put several layers of tape over the crystal and you should be ok. Do this at your own risk of course.
That’s pretty much how I do it, although I would add a few bigger “abrasives” just to give some inconsistencies and randomness to the aging…bigger screws or bolts, rocks, coins, etc.
I also like to polish the watch a bit between sessions of “abuse,” to replicate a few decades of service every couple years, by the local watch smith. They weren’t as concerned with keeping things like they left the factory back when these were just “tool watches” and not museum pieces. And lots of the mom and pop shops loved to make them shiny, lol.
Very few were making the trip to the big city every time dads old watch needed a service to ensure that the AD did it right. At best, they’d take it to a department store, where the jeweler/watch smith might have had some factory training materials on hand.
The point is, you have to decide if you want the watch to look mint, “aged” in the way someone would own it today, or do you want to replicate the real life most of these watches actually lived?
