I've been collecting pocketwatches for many years now. I probably have about 40 of them. Mostly American made railroad grade but I also have a few swiss and some Seiko's all mechanical. I usually carry a Hamilton model 950 made around 1910. I can't remember the last time I had to set it, probably for the changeover to daylight savings time. Its more accurate than most modern quartz timepieces.
If your looking to buy one a search on google for pocketwatches will return many hits. One place to check out is www.oldwatch.com he's in Oklahoma City and though a little on the high side has a very good selection and if you stay away from the real high grade stuff you can get something reasonable for a descent price. You should get a copy of complete price guide to watches by cooksy, shugart its the bible for these things and the first half is devoted to pocketwatches and the first 150 pages or so is a crash course on pocketwatches.
If you have any specific questions I'll be glad to help you out.