mower,
yes, but if they use the higher grade 316 stainless, it maybe tricky. Stainless steel is hard to work with because of its physical properties. If you feed the drill to fast, the bit will burn and actually harden the stainless steel, making it very tough to drill through again.
Other than that, drilling and tapping is no problem. I was hoping to get a second case so that I can experiment on it first before risking actual watch case.
For those DIY attempting to do this. I recommend you buy Cobalt drill bits. They are better for SS.