Oldest I can confirm is an Elgin from 1944/1945 based on serial. Sadly doesn't run. I need to service it.
Potentially the oldest is my Jaeger DuoPlan, advertised as a 1931. Jeager wants close to what I paid for the watch to pull the records, so I can't confirm the year. It does run, though. I wear it occasionally.
Breitlings, like many high-end watches, should have some sort of serial number on the back or on the mech. Take a look for that.
Vintage electric Hamilton Ventura, cal. 500 from when they were American made. I know I could go get one of the modern Swiss-made ones in auto or quartz. Not the same to me, though.
That or something from Jon of York.
I fully understand watches are a luxury item. The community seems completely out-of-touch with what constitutes 'reasonable money' or 'low-end.'
That's generally my opinion on most collectible markets anymore, though. So, what the fuck do I know?