Some I've passed up and really been disappointed in myself for doing so were. Double-barrelled Luftwaffe pistol the guy wanted 475 that was like 1999 or so. At the time I was upgrading many things as the internet was new so I passed.
And about 10 years ago a Japanese triple barrel. the collector was a huge Japanese collector from South Dakota. He was a truck driver by trade but he had a crazy passion for Japanese things. The triple barrel is very unique and at the time he only displayed it. But after he died the family sold it and everything off. I missed it. Only got one piece from his collection. Which was ok I was into buying bicycles then anyway. The old guy took me in as one of his own on the gun show rounds. when he treated most people with distain. He was rough for sure. It's just stuff anyway man! That's one thing I've learned I'd you think you want it and you have the funds buy it. It will be gone in short order. Flip side is if you don't sell it your family will after your gone. When to draw the line is the trick. I been to both sides. Laying in a hospital bed telling your wife what's worth what and who to sell to.
Bret