Offcenter Strikes (Error Coins)

@andi, based on the coins posted here, it seems as though world coin errors are more thinly collected. However, there is for sure a US-centric bias that accounts for at least some of the discrepancy.

Another two price lists, again US centric https://coins.thefuntimesguide.com/...error-coins/ and https://coinsite.com/us-error-coin-values/

From John Sullivan: Virtually all series of U.S. coins are known with off-center strikes. Some of the rarest types include series that were short lived or had low mintages generally, such as the Flying Eagle cent, 20 Cent Piece, 3 Cent Silver, and any coin types which were struck with extra care, including proof coins or gold coins. Finding even a 5% off-center strike on series such as these can be very difficult and finding a 50% off-center example may well be impossible.

Modern coins are common with off-center strikes. Lincoln Cents, Jefferson nickels, Washington quarters, and most coins minted since the 1960s for general circulation are usually common as off-center strikes. The rarities in these more modern series of off-centers are certain dates and mint marks. Learning which are rare takes time, and generally involves asking an expert on the series or simply doing careful research into auction records. (note: which is where I summarized before and seems to be agreed by tdziemia).

One other rule of thumb with off-center strikes (and for almost all mint error types) is that the larger the coin or denomination, the scarcer the error is. For example, Lincoln Cents and Roosevelt dimes are generally very common as off-center strikes. Eisenhower dollars and Kennedy half dollars are scarcer. This rule of thumb applies to older coins as well. (Maybe that info will be useful in translating to foreign if someone hasnt already made pricing lists for them)

A collection of off-center strikes may be formed by date and mint for a particular series of coin (such as collecting off-center Lincoln Memorial Cents from 1959 through 2008) by date and mint mark, or perhaps doing a type set of off-centers, such as a 20th-century set formed of one coin for each design and metal type. Off-center strikes are popular due to their often-dramatic appearance, easy to understand manner of production, and also because they tend to be one of the most affordable error types. https://www.PCGS.com/news/the-popul...enter-strike

Coinweek articles on off center errors, one sold for 79k!
https://www.coinworld.com/news/us-c...rs-want.html
https://coinweek.com/coins/error-co...nter-strike/

Well, providing more detailed scope of your question is more helpful than being "general".

In a recent Pegasus auction, several slabbed mint state 5 - 15 Bani coins ranging from 5% to 25% OC were auctioned at starting price of 150 - 250 eu.
Only the lowest priced specimen sold: https://www.numisbids.com/n.php?p=l...5534&lot=871

In another auction, a 1946 2000 Lei coin at 5% OC, and slabbed by NGC sold for 310 eu.

So certainly there is a market for these errors on modern Romanian coins, at fairly attractive prices (though you need to figure in the price to have them slabbed).

Probably your own research already found these examples.

I do not see evidence that minor OC adds any value to 18th century Swedish coins, but I could find only a little data.

What did your research tell you on this?