It was noted in a thread that, when traveling,
a) don't pack watches in checked baggage
b) pretty often, you won't need to take more than 2 or 3
So I started looking for something that would work. Criteria:
--hard shell...aluminum, steel, or EVA
--inexpensive...I'm not going to need it that often, and really, who else is ever going to see this?
So...the aluminum RFID card wallets are a potential choice. I have one that I could use, and may yet modify. Size is perfect. On mine, the accordion card holder looks to be easily removable, albeit NOT reversibly. Something like a felt lining...Hobby Lobby carries felt squares...and more felt to pad/separate between the halves. This should work.
Check on Amazon. After a while, it dawned...hey, there are cases for portable hard drives, for GPS, for point and shoot cameras. Man, SOMETHING should work.
Yep. A camera case.
One watch per section; throw in, say, a microfiber cloth, of the kind used to clean eyeglasses, or phone/tablet screens, or cotton felt to go between them. The heck with carry-on, this will fit into a pocket. :)