The glass on a wristwatch can become cloudy and scratched-up with usage over the years. An easy fix for this is to buy diamond polishing compound and clean it up yourself, as this guide on Imgur shows.
The guide uses 0.25 micron and 3 micron diamond polishing compound, but you can get a set of 1, 3 and 6 micron on Amazon for $ 26. You’ll need to apply the compound for a good two hours, so make sure you have the time.
DIY Watch Repair | Imgur