Later...I don't know the "how, or why, but I now see both coins in relief! Befor, the left one was incuse! so much for vision. Or should I call it an "illusiion"?
My first observation is that the "coin" on the left is not a coin. It is incuse, while the coin on the right is relief. it appears to have been pressed into softer metal, which would all w a "clash-like impression to be made, except the two would be reversed. (This case indicartes a two-step procedure, which would change the "working hub" into a master hub, which would be in relief, as opposed to being incuse for the final striking of the coin, in relief, or in cuse. Depends of the design), as appears in the two shown. Second, the fonts are not the same, The 0 in 10 is not the same on both images. My vision does not allow much more scrutiny, than that I noted. What is the third difference?
In answer to what is an error, as opposed to a variety? The error is transferred from the working DIE, to EVERY coin struck by this die. The variety, is something that changes form A single coin, to the next coin, or coins. It is NOT a constant, as is the ERROR. Crudely expressed, but essenctially correct. Not being up to date on most world coins, the two shown could both be coins, normally used.
I do believe the coin on the right was made with worn dies, as indicated by some extra lines next to some of the letters, or devices. That does not mak it an error, nor a variety. The making if the hubs is where the error is introduced, usually. The variety, will be caused by the presses, during the minting process, mmaking varietied.
2. who decides? that is a matter of when, not who. errors are produced by the working hub, if an arror is present in the HUB. tjhe vatiety is determined by 'chance, depending on the stat of the equipment during the minting peocess.
3. who set s pricing? Thre first one sold, or bought is decided by the buyel, and seller. All other prices are just "adjustments of that figure.
4. why some are more 'pricy" than others? many reasons, such as Mintage "supply and demand", need for commerce, among others.
5. why are some recognized by others, despire clearly being different? Look at it thios way: You are NOT a coin collector. Some one shows you a coin with both a HUB doubling, and a
Mechanical Doubling. would you know the difference?
Dick