I have dozens of them and everything what concerns the technical development. Timex had made about 1 billion watches between 1950 and 1980, that’s about 135,000 watches every day, calculated on the number of working days in the year. They were reliable, cheap and good work horses. Cheap and good work horses means, that they have been worn and used, the were no collectors items. That is why you don't find so many vintage watches in best shape, despite the large number produced.
Don't go for that 10- to 20- dollar crap, even if the watch is still running. There are mostly beat up and filthy (Of course with many exceptions to that rule). Not seldom, you can see watches of Timex in very good shape at garage sales, often for one dollar or two. At this extremely low price level compared to other vintage watches, add a few dollars, even double or triple the money you want to pay for, and get something good. From time to time you can even find NOS- (new old stock) watches which have not been sold or worn for some reason or have been kept in pristine condition. I have no problem paying 100 dollars plus customs plus shipment for a Timex in mint condition, depending on the model.
Next thing to do, get yourself acquainted with Timex watches. You will find all the technical stages of wrist watches, from pure mechanical, electric - where just the motor with a battery had replaced the power spring, with the rest still mechanical -, electronic (same thing as electric, but with solid state components), Dynabeat (electric with higher vibrational frequency, quartz analogue display, quartz with LED and LCD display. The only thing Timex has skipped was the tuning fork watch, as they did not, like all the others, work under the Bulova license. Then you have no date, date, date and weekday. Electric and electronic watches are however difficult, if at all serviceable, and the cost, compared to the value of the watch, is never justifiable, if you are not dealing with a family heirloom.
The movements are very simple and usually not worth a repair. The watch had been simply thrown away when there was a defect. You still find many movements on the market and there were not so many different models.
You can also get cult-watches like the model the Blues Brothers were wearing etc.
So, summing up my recommendations:
1. Get yourself acquainted with the vintage Timex models. Timex has a very good number system on the dial, allowing you to immediately date the watch, no guessing around.
2. Select certain watches, like electric or electronic for example. They are highly interesting from a technical point of view and most watch collectors, especially the younger ones, never heard of them and the others often don’t know what kind of animal they exactly are or what the difference is between electric and electronic.
3. Don’t go for trash, they are cheap enough. One good Timex in good condition is worth more than a pile of beaten up specimens, and they get – no they must get – ever rarer, although they will never be a collectors dream.
4. Look for original Timex ads from the time period, perhaps showing your watch. There are many around and can complete your collection, like Timex display stands, boxes etc., all available for a song.
Last, but not least: Timex watches have been made all over the world. At the beginning of the electric watches, Timex had bought the German company Laco because of the technical know how they had in this field. You find them with Laco on the dial and later with Timex made in Germany. I have some watches made in Scotland. The plant had to be closed by Timex because of a very violent and long lasting strike, never again matched in this magnitude in the UK- Braveheart at the picket line.
Below: movement electric and electronic, watch and ad Timex Electronic 1971 by Laco