One of my preferred dealers. His list prices tend to be high, but he usually negotiates in person. His in house watchmaker services everything beforehand. https://fathertimeantiques.com/index.php
If you have a more specific question, I may be able to give a better answer. The following is for pocket watches. I don't have much recent experience with vintage wristwatches but much of this answer will transfer. I'm assuming you are asking about circumstances where the provenance/history from new is unknown/unprovable. If you don't have experience, you need to buy it from someone very reputable that you trust. A little knowledge about what you are buying will also help a lot - so you can ask the right questions (important, even with a reputable dealer). It also depends on what type of vintage watch. In the case of pocket watches, the provenance can give you a value boost but because they aren't trendy/fashionable even the best still cost pennies on the dollar compared to wristwatches. Things like Patek pocket watches are like vintage Ferraris: the movement number is engraved into the case (and box and papers, even the old ones, are also more likely to have these retained - my minute repeater is 110 years old and has the full set). This was also the case for super high end American watches (which were pretty much on par with Patek - John Jacob Astor was wearing a 19 Jewel, 14K Waltham when he died on the Titanic). American pocket watches are designed to be generally standardized across brands and have movements that are interchangeable with cases. Which is why gold filled cases are so common - same basic look, much more robust, much less expensive and readily replaceable when worn out. Until the 1920s you would go to the jeweler and pick a movement and case, and possibly the dial and hands, then the jeweler (or his watchmaker) would assemble them for you. I don't have any pre-1920 American railroad grade watches with the original jeweler's receipt (the factory box wasn't a 'thing' for work or regular watches). This changed for very high end railroad watches in the 1920s. I do have a few sets for 1930s and newer but they are (mostly) underwhelming for the premium you will pay. Certain brands would have a set-up with the whole package, similar to a modern Rolex but more compact and nicer (e.g. 'Keystone' Howard) but this was usually for smaller (10 - 12 size) vest watches (like the Hamilton 921 movement that RGM is now re-casing as cool but expensive wristwatches). The documents will list the serial numbers and confirm the match. The basic way to check an American watch without papers is to first look at the watch to determine if it 'looks' correct - should the case, dial, hands movement go together based on the grade of movement and period? The second is to open the watch and look at the movement, it is retained in the case by case screws (usually 2, holding the movement to the inner lip of the case). If the case had a different movement in it previously, there may be 'telltales' of other case screws in other locations elsewhere around the case lip. Things become slightly easier in the 1920s when the manufacturers began supplying complete watches. For example, I have a very early 1920 17 Size Illinois Watch Co., Sangamo Special (their top if the line) the case and movement are correct, original to one another and mint, but the mint dial and hands are, stylistically, from Sangamo Special watches sold a few months earlier - I'm trying to research if they are replacements or if this is a transitional piece. These 'cased and timed at the factory' watches are a bit easier to get right as the options are known. On American railroad watches, the standards are sort of like concourse standards on repainting a vintage Ferrari: Not only is repainting allowed, you can make a color change to another color that was available from the factory when the car was new. For American railroad watches, this standard is 'could/would the watch have come from the factory like this?' This is a practical concession as the case and movement serial numbers aren't supposed to match and most factory records, along with the American watch industry, are long gone. On the other side, if the watch was designed as a 'work watch' with hard use intended and a parts system that was created for long term support and for easy maintenance/replacement, and the 100 year old watch is correct for how it would have looked after 20 years of use (replaced case and all) while keeping time as well as a modern mechanical watch, it may not be worth worrying about. Personally, I like both factory original or correct for a certain period but I also know what I'm looking at - which makes it more fun. BTW, those 'perfect' vintage Rolexes with 'tropical' dials (aged in a certain way) may be correct but may not be 100% original either. Regards, Art S.
Love the shop's name - it's an Elgin model. He's got some nice pocket watches. The Hamilton 950E is neat (just before WWII) and I love Elgin 'convertible' with the multi-color lighthouse case! The lighthouse watch may not be too far above gold spot price now. Regards, Art S.