I’m genuinely curious as to how PSA finds/ searches for auctioned/ sold PSA graded cards on Ebay or other auction houses.
Do they do some NSA Algorithm level stuff or something a lot more simple?
I am asking because I’m checking out some auction prices on PSA’s website and saw that they are missing some listings
(the ones that I won)
(as you can see, I’m not too tech savvy) 
This question may have been answered before so if there is a thread, please link me below!
@pierce would probably know as he designed his own site to fetch auction data. I guess I’m not positive on whether he fetches it just from PSA or from PSA + eBay.
I should have mentioned the site is pokemonprice.com and is linked at the top of the forum. IMO it is a far superior tool for past auctions than PSA’s site.
The data comes from the PSA site.
Most likely PSA is monitoring certain search phrases and is scraping item listings or has an agreement with Ebay to use some internal, more sophisticated search algorithm than what is publicly available through their site.
Almost certainly, they are using the barcode in the image to identify the card (possibly in combination with identification of the actual characters in the serial number), so if the label is obscured or unreadable it will likely not get documented.
I wondered how PSA/Pierce dealt with the incorrect listings. When I pulled the Charizard 1st PSA 10 chart I noticed there were a couple incorrect data points. I figure that would happen as there are many mislabelled auctions. Here is the chart for reference, the incorrect points are around march/april:
When I worked in institutional research, we had to manually scrub data to work around these types of problems. I’d guess it’s a real challenge to do that in real time.
I’ll fix those - as @pkmnflyingmaster linked if anyone sees data that is incorrect or missing you can submit it here pokemonprice.com/SubmitData. It only takes a few seconds and is really helpful, in the future I’ll try to automatically flag things like this and alert me if a price deviates too far from the median so I don’t have to rely on the community notifying me.
Most of the incorrect data points come from auctions that sell groups of cards and PSAs algorithm wrongly interprets it as an auction for a single card, that or foreign language cards getting recorded as English. As the tech is automated and there are a lot of nuances it’s far from perfect but it does a great job the vast majority of the time.
I’ve mentioned it before but I get my data from PSAs website, and as @pkmnflyingmaster also mentioned (he seems quite smart) they probably have a function that searches eBay via keywords and uses image recognition to read the barcode and match a card to it’s database, which would explain why card lots where the first image is a single card that is also mentioned in the auction title always get recorded incorrectly.
The site I feel has better data than PSA’s auction price realized because I get a lot of submitted auction links for big auctions that PSA misses, eg. A lot of the PSA 10 1st edition charizard, shadowless, 1st edition PSA holos were all user submitted because PSA missed them, but they’re in pokemonprice.com’s database 
I also remove all the incorrect data pretty quickly as it’s found or reported.
I’d remove those two low amounts in the above graph cause they weren’t legit.
I submitted the removal for those low two data points. The sub 10k is obviously fake. The 15k eBay auction was actually still viewable. The seller has 50% positive feedback and took someone’s photos and tried to scam to no avail.
pokemonprice.com/CardDetails/73864578-8b54-4422-a77f-96601c47a549/charizard-holo-1st-edition 
Looks a bit nicer now doesn’t it?
