You see a lot of these older Citizens and Seikos coming from the Philippines, and they are rarely original. Another reason to get a movement shot is that most of the ones that come from the Philippines have at least some pitting on the inside from corrosion, either on the case, or the rotor, or both.
Back before I knew better, I bought several, only to find that half the parts were aftermarket, and they had corrosion inside.
This is my advice for anyone looking to buy a vintage watch online:
Do your research: If the watch in question has a model number on the back or on the dial, run a web search for it, making sure to put the number in quotes so that it doesn't just find similar ones. This advice is typically useful for Japanese brands like Seiko, Citizen, and Orient, with Seiko likely having the best results. If an image search turns up a ton of watches that look like each other and not like the one you're looking to buy, keep walking. If it's a popular model like, for example, a Seiko 6309 diver, learn to spot the "tells" in aftermarket parts, such as the straight-edged day/date window on many aftermarket 6309 dials. It's not perfect (won't help you spot a redial, for example) but it will help you weed out some obvious problem watches.
Learn to spot the big things: Get movement pictures, and learn how to spot dirty, modified, or improperly replaced movements. Learn how certain complications work; avoid non-working slide rules, tachymeters on non-chrongraph seconds hands, worldtimers that don't have very clear hour markings. If a watch has specialty markings on it (military issue markings, brand markings like a Seiko Scubapro, etc) be thorough, as these can be more desirable and thus more often faked. If a dial has a matte (or "flat") coloration, especially in outrageous colors like pink, orange, or teal, move on. I've mostly seen these out of India, and they're usually bargin-priced Citizens, Seikos, or Orients, although I've seen a few supposed Longines and Omegas redialed in this fashion. If your prospective Russian watch has German military vehicles on the dial, run.
Learn to spot the small things: It's harder to determine when hands are wrong than it is for dials, but it can be done. Again, research helps here. Watch the quality of dial printing; if it seems too fat or gloppy you might be looking at a redial. If the watch has a bezel, check to see if the insert is proper; right font, right markers. If the watch has a day/date complication, see if the color of the day and date wheels is the same, as a mismatch could mean that one has been replaced. Any little detail that catches your eye and strikes you as potentially wrong is worth further examination.
Wear is your friend: Faking the passage of time is difficult. A few dings and scrapes or a slight bit of corrosion can tell you that that one part, at least, is old. A photograph of another example of your prospective watch all beat to hell can be a real boon, since that can tell you that it's an original.
There are exceptions to many things I have said above: Developing a good sense of what's good and what's bad takes time. Some of the guidelines I've listed above have their exceptions, and it takes time and study to learn them. I know I certainly don't know them all yet.
Here's an example. I saw this Citizen diver listed in an Ebay auction, with India as the seller's location.
The auction advertised it as a "rare" Citizen diver, but as we all know "rare" in an auction listing is effectively meaningless. The price was right, but several things struck me as slightly off:
The green color of the lume is unusual.
The seconds hand is white while the hour and minute hands are silver.
There's a desirable mark on the dial (the broad arrow you see on Promasters and the like.)
The water resist is written in a somewhat unusual "20bar" form.
You can't see it in this picture, but the crown is quite small for the case.
In addition, I had seen this style of dial and hands used before on 150m Citizen divers branded with either the "CQ" or "Crystron" marks.
I immediately looked at the caseback pictures, and came up with a possible model number - 3802-451732. This search turned up several examples of the watch above, some for sale in good shape from places other than India, and others absolutely beat to hell. From this research I was able to determine the following:
The green lume is normal, although it can apparently fade to a whiteish-grey.
The seconds hand is, oddly enough, correct. (When I got the watch, I immediately understood why - a silver hand wouldn't be nearly as visible.)
The broadarrow and "20bar" notations are correct; the 150m CQ divers have a different model number
The small crown is proper for this watch.
The bezel insert, with hash marks all around and thicker ones from 12:00 to 4:00 is correct.
One source described the watch as an early Promaster, although I couldn't verify this.
In addition, I also found references to a 3802-451741, which is the same watch with a Pepsi bezel.
All of this, combined with slight wear to the bezel and crystal, assuaged my doubts and I bought the watch. Having received it, I do wonder whether the day or date wheel has been replaced at some point, and I have determined that the drilled lugs were a modification done for an earlier owner. But I still think I got a good watch at a good price by doing some research and taking a chance.
I wonder if there should be a go-to thread about evaluating affordable vintage watches in this forum?