I think we've all done it. You take up a new hobby or interest, you get far too excited and either buy something for over the odds, or that's not quite right - only to discover down the line the error of your ways. For me, it was an Omega Polaris Titane - I love this watch, I'd always wanted one, and there it was on eBay. Without looking at the pictures properly, or doing enough research, I'd bought it - only to discover down the line that the the clasp isn't Titanium (swapped out by a previous owner, probably because the Titanium clasp broke and the steel was a much cheaper replacement), and neither is the case back (swapped for steel so that it could be easily engraved...). Thankfully I'd not dropped a lot of money into it, and I like the watch. So that's me... how about you lot? ;-)
I bought a so called '18K' geneve when I was very new to buying vintage, needless to say it was one of those god awful 60's/ 70's fakes but thankfully the seller was also unaware and refunded me immediately! Other that it's just been the usual fleabay robbers gazumping me and never sending me the watch they pretending they posted it!
Thanks to the people on this site I'm 1 for 1, but am sure I'll make some regrettable buys in the future.....I know me.
My first purchase almost turned me away from vintage watches completely. I was looking for a Tudor Submariner on eBay and randomly came across a 1940's Heuer chronograph that looked to be in amazing condition. I was completely unprepared and hadn't done any research (truthfully, didn't really grasp how much research you have to do when preparing to buy a vintage watch), and my wife said "just buy it!" when I asked what she thought. Long story short, the watch arrived, I re-posted a few pics of it in the forums, a nice member pointed out some rust in the movement pic and soon after, my local watchmaker quoted me at $800 to service the movement. Also, the dial had been re-painted but I paid full value anyways. Thankfully the guy took back the watch after I argued that the movement should've been noted as such in the listing, but some strong words were exchanged. I've gotten better since then though! Learning from mistakes is the best way sometimes.
About 8 years ago I bought a '70s Seamaster at a flea market which actually turned out to be a Geneve with a Seamaster re-dial. It only cost me $120 and I gave it to a mate who loves it. I didn't have any way to open the caseback at the market and the re-dial actually looks pretty good without a loupe, I only realised when I got home. I actually wish now that I'd bought the NOS SM200 parts which were pretty cheap at the time and pillaged the cal 1012 out of this watch instead of giving it to my mate.