WOW! With that kind of documentation, I'd say grab it if you can afford it! With a mintage of only 800 proofs and a PCGS population of only 19 in this grade (only 11 higher; this is for comparison with the NGC popn report), I'd say it's a good investment. PCGS Price Guide puts it at $2750 which is his asking price. Usually, PCGS Price Guides are on the high side, but with a coin that is uncommon, it's gonna go up in value and will cost more down the road when one comes available. If it fits into your collection, I'd say that you probably aren't gonna see too many Proof-65 1888s available, so now would be a good opportunity to grab it if it's what you want.
Although I've never done business with Anaconda, it has a good reputation and his feedback is almost perfect (only one withdrawn and that was an error in the first place). Solid return policy. I don't see any red flags or even yellow flags on the auction, so you're not gonna be ripped off.
You could put in a Best Offer below the $2750 and take your chances, but if it were me and I really wanted the coin, I'd go for the BIN option.
Many thanks for posting the auction. It clarified everything and removed all doubt about this quarter. Good sighting!
Fred