This question is impossible to answer...there are many of them with very low mintage known.... stainless
You don't get any rarer than unique. The 1870-S Half Dime, 1870-S $3 and 1873-CC Dime 'No Arrows' are unique.
I don't know about world coins but with one known example each, the following would qualify as the rarest United States coins: 1866 Seated Liberty Half (with no "IN GOD WE TRUST") 1851-O Seated Liberty Dollar 1870-S $3 Gold Piece You might also include the 1959 Lincoln Cent with the Wheat reverse with one known. There are probably hundreds of non-U.S. coins with only a single examply known.
Like said earlier, this question is almost impossible to answer, lol. Atleast in my opinion. Would we include errors and varieties in, or just a "normal" coin? And what would we do to consider rarity? Mintage? Price? Condition? Most desirable? Etc? I'm not trying to being snotty, or rude, lol, but these are questions we need to think about, and ask, if we are going to guess at the rarest coin in the world. Phoenix
The 1959 Wheat cent is controversial, never been authenticated solid and sold with an archive. Experts disagree on it. Add the 1917 Matte Proof Lincoln as well. Brasher Dabloon ( spelling, sorry ) was the highest ranking coin for many many years. There are over a dozen '33 Dbl Eagles, check the Langborn suit. I think Hobo nailed this one.
People, if you talk about world coins, I believe every european countries have a bunch of coins of which only one exemplar is known (at least I know Portugal does). What can be rarer than that? Half a coin, maybe (as is the case with some ancients).
There are numerous coins where only one example was produced. This year alone I handled several. I also handled probably around 100 coins were the entire mintage was 10 or less. Rarity doesn't mean much with many world coins.
Probably US wise. :whistle: World and Ancient coins, that is a whole different ballpark, (as you yourself probably already know, lol.) Phoenix
When you pay seven plus million dollars for a 1933 $20 gold eagle that kind of puts it up on top of the pile. I know there are coins of lower mintages etc. but that kind of money does make it rare. Considering that the Secret Service considers them stolen from the mint. Ice
The question was "What is the world's rarest coin?" not "What is the world's most expensive coin?" I named 3 examples of unique US coins. When there is only one known example (the very definition of unique) you cannot get any more rare than that. OK, technically, the 1964 Peace Dollar is more rare than unique because there are ZERO known examples. I'll grant you that the 1933 Double Eagle that sold for seven figures was "unique" at the time of the sale. But since the sale 10 more examples have surfaced. That makes 11 known examples. I still say unique - 1 known example - is more rare than 11.