If that is the fortunate position you find yourself in, then you should probably endeavour to get a small number of good pieces for a fair price, rather than a lot of possibly dubious ones for less money. If you did have the wool pulled over your eyes, then you are certainly not alone and as annoying as it is, nothing like that is ever an experience wasted if you become wiser as a result of it.
It's good advice on this thread with regard to authenticity, probably the only genuine provenance you will find is one that you can be pretty sure is indisputable, such as a relative or known family friend of someone connected with an item in some way. And the likelihood of people selling things which have a family legacy attached to them is always going to be slim, so that notion alone is indicative of how likely much of what is available could be faked.
For example, I have some parts from a MiG 29 which was one of two that collided at an airshow in the UK when both pilots ejected, this incident...
Most of the parts are really little more than bits of bent metal with cyrilic lettering on them, and that probably would not be hard to fake, but I got those from my friend who worked at the place as a technician, he was in the RAF at the time, and his job was to service ejector seats, so the wreckage came to where he worked in connection with the investigation into the performance of the Russian ejector seats in that crash. After the investigation ended, he got the bits and gave some to me. That's the kind of connection you cannot dispute. I have quite a few bits from modern jets from him, such as drogue chutes and firing handles from ejector seats etc, which of course I know to be the real deal simply because of how I came about them.
Another thing worth bearing in mind is the object itself. Some things are definitely going to be hard or next to impossible to fake without going to massive trouble, such as a part from an engine that can be compared to a complete item. Items such as this, which is the firing handle from the ejector seat of one of those MiG 29s:
So another source worth checking out is the aircraft parts market for vintage craft, as that is where many genuine items that would be hard to fake might show up, and their authenticity is likely to be beyond doubt. Many aircraft parts are time limited, or no longer airworthy, or the remnants from several items sourced to make a complete working part or whatever, so that would be a genuine reason for such items to be on sale. Keep in mind too that dealers of such collectible stuff do not limit themselves to one era or type, so it can sometimes be worth getting hold of something not from your era of interest if it is rare and the price is good, since that's something you might trade for an item you are after.
Al