Here are several mechanisms from inexpensive mechanical watches of relatively low quality:
You can find some good quality watches for very low prices among ladies' watches because many collectors do not want them:
Here are two electro-mechanical watches. They were quite expensive in their day but can be found very inexpensively today. They are interesting watches for the collector on a tight budget.
You can find some early quartz watches for very low prices, though they were extremely expensive in the early 1970s. The Girard Perreggaux 352 was one of the first Swiss quartz watches offered for sale to the public around 1969. The Bulova Accutron Quartz watch shows that it was produced in May of 1969. For comparison, the first Seiko quartz watch, the Seiko Astron, cost $1,250, as much as a Toyota Corolla in 1969. These early quartz watches are pieces of history. I feel they are undervalued at the moment, and will become of interest to collectors soon.
These watches marked the beginning of what collectors now call the Quartz Crisis. The truth is, however, that quartz watches were more reliable and accurate. When the prices came down, quartz watches became affordable to the average consumer. Never before has accurate timekeeping been available for such low cost and to so many people, thereby having as great an impact on society as the Dollar Watch had once had, decades earlier.
You might find some relatively good quartz watches, like this Seiko, made between 1980 and 1985. This watch has metal gears and metal plates.
However, you might buy a watch that you think is good, but find it has a small inexpensive mechanism inside, like this quartz diver's watch. Buyer beware!
Many quartz watches made after about 1990 have very inexpensive plastic mechanisms that should be avoided.
Notice how the case has corroded: this is why you should avoid "base metal bezel" and look for "stainless steel" instead.