Aaaand... uploaded!
(It took at least half a minute per file, though, and I was really worried that it wouldn't work anyway, because the file sizes were very close to 300 KB, and CCF likes to make them slightly larger.)
The actual writeup follows...
I wasn't answering for a while because my clear front-runner was a bullion Maria Theresa thaler, which is a type that had already been posted by @arkie (though my example is less worn and/or better struck) - and I couldn't think of a good second place... and, for that matter, couldn't find most of the second-place candidate coins I
did think of, anyway.
But then I thought of a nice scenario with a
different front-runner...
...It was October 2002, I was ten years old (nearly eleven - though I looked a lot younger than that, and regularly took advantage of it to buy cheaper kid tickets), and my mother took me on a vacation (organized by her former classmate, and also featuring said classmate's much larger family) to Sevastopol, then firmly in the Ukraine (though still mostly Russian speaking).
Obviously, once in Sevastopol, we tried our best to visit the city's main tourist attractions...
As most people of Soviet cultural heritage probably know (which admittedly probably doesn't include many people here), some of the Land of Fools scenes of
the 1975 live-action Buratino movie were shot in Sevastopol.
The specific shooting location of the Field of Wonders eventually became a tourist attraction; admittedly, being also the site of medieval
Cherson, it probably would have ended up as one anyway.
As such, as a somewhat impressionable 10-year-old boy, I was successfully persuaded to bury a few Ukrainian coins at the ground of the Field of Wonders.
Maybe, I was told, by the time of my next visit (then expected in a year) there would actually be a money tree on that place, with hryvnia coins growing on it?
(As far as we were concerned at the time, hryvnia coins were an urban legend - we were occasionally told that they exist, but not many people had actually seen one, and we definitely didn't.
They did exist, as we later found out, but were apparently at least as rare as US half dollars.)
...The expected 2003 visit to Sevastopol ended up getting called off at some point, and ultimately I never actually returned there.
(Given the recent unpleasantness in that area, I don't expect to get there anytime soon either.)
But ever since, I occasionally wondered - what kind of coins
would be growing on that tree, had it actually appeared?
Presumably something Ukrainian - almost certainly with a large denomination - and, given that it's the Land of Fools after all, probably completely useless...
...hey.

Ukraine, 200,000 karbovantsev 1996, commemorating the 10th anniversary of the Chernobyl disaster.
Never intended to circulate, this coin was demonetized shortly after issue anyway.
(Bonus points for featuring a bell - as the main attraction of the Cherson area of Sevastopol is, in fact,
a bell; a completely different one, obviously.)