This is going to sound weird.. But Timex is killing it right now..
The Timex M79 is impossible to find.. originally priced at $279 it's going for ~$600 on the used market.
If you are looking for VERY UNDERSTATED.. The Timex American Documents watch is a new classic. (~$500)
I'm an omega guy... So i would always recommend them. Its at the top of your list, but the older style Seamaster 300 Pro is an awesome watch that will continue to go up in value. Its also the Pierce Brosnan James Bond 007 watch 🙂
(~$1,800 used)
I can go on and on and on 🙂