Watch out for ads where the seller states that their old watch "might run, but they are afraid to wind it", or they "can't get the watch open" to tell you the serial number on the movement. I would venture to guess that over ninety percent of watches that "they" are afraid to wind, DO NOT RUN AT ALL! Almost all antique watches have either a screw on or a pop off back. Do not bother to list the serial number in the case on watches, it means absolutely nothing! The movement number (where the gears and wheels are) is the key to finding out when the watch was made, and in the case of Elgin watches, everything else about them. Another thing to watch for is the seller who states that "they shook the watch and it ticked for a few seconds, or a minute or two. Shaking the larger size antique pocket watches can break the balance staff and render the watch useless until a new staff is located and installed, and this is a real chore! To the best of my knowledge there are no manufacturers making replacement staffs for the old watches. So it becomes a real crap shoot, finding a staff, in most cases having to modify it to fit the movement you are working on, and trying to explain to the customer why their $45.00 clean and oil job just climbed past a hundred dollars. Be aware of watches that have a missing balance wheel or hairspring, the chances of finding a replacement are slim to none! Also the hairpin spring was matched to the wheel and finding a replacement that works is another nightmare. In our shop we have drawers full of old movements, wheels and plates galore, but very few balance wheels with a good staff and hairspring.