The vintage watches which have staying power in the collecting field are Patek Philippe, Cartier, Vacheron and Constantin, Audemars Piguet and Lange. Also Rolex watches from the thirties and forties with automatic movements and "bubble" shaped backs.
Look especially for the complicated watches, -those with stop watch functions, moon phase indications or perpetual calendars. The more functions, the less important the manufacturer's name. Otherwise square styles seem to be more sought after than round ones.
Unless you know that there is a specific reason why there should be no name on one part, always check the dial, case and movement for names prior to purchase. Exceptions are retailers like Cartier which used European Watch And Clock Co. movements and watches which were cased by the company's American importer. This was done with the full authorisation of the factory during the first half of this century to avoid heavy American import duties.
Most new wrist watches probably do not have much immediate investment potential. It is unlikely that any quartz watch will ever be worth much. The established brand names which were always regarded in the past as being the best watches made (such as Patek Philippe, Vacheron & Constantin, Audemars Piguet and Blancpain) probably sell their standard models for about as much as they will be worth either now or in the near future.
However it is possible to get today's watches with investment potential as long, obviously, as one doesn't overpay.
A significantly higher quality product is made by craftsmen often farmers working in winter in the Vallee de Joux in Switzerland. Their minuscule production is sold to the watch companies for sale under those companies' own names. The names of the craftsmen is only known to the watch companies themselves, and can only be found (or, more often, can't be found -by the collector at any rate) buried deep in their records. Very occasionally there is a clue on the dial, such as a round mark opposite the subsidiary dial which contains the name of the watch company, sometimes with an observatory certification.
The only company which habitually sells significantly more watches of this calibre under it's own name than normal production, is Breguet. Otherwise the watches are sold as specials by Audemars, and a few by Patek, and Vacheron, where they are of very limited supply. Unfortunately they are commensurately difficult to find, either new or old. They can sometimes be identified merely by the knowledge that the particular watch being offered is new but is not in the companies' catalogue. Salesmen may wrongly think that the company did actually make the watch itself alongside other high calibre special movements.
Lastly do not take vintage watches to a local jeweler for any restoration beyond a simple cleaning.