How Is A Die Variety Confirmed?

It only takes one. Any coin that can be confirmed to be a die variety and also can be confirmed as not already listed can be listed with a new die number. Limitations to this include coins that are too low grade to determine and coins that do not show markers. These will usually be ruled out.

By the way, anyone who attributes die varieties properly uses about the same methodology - it's not rocket science, and there really aren't a lot of different ways it can be done.

Markers are only inductive of die states of varieties. EDS (Early Die States) may not have developed markers that would identify later die states. So if you search looking for markers rather than the correct way then with the dies going through the same thing over and over, die flow/die wear/die clashes/die cracks only identify the same die state that a coin is listed in a publication or book. The real determining of a certain die is Separation of the hubbing/RPMs and Location near other devices on the coin. So separation/direction, Location (mainly for RPMs although doubled dies may have mint marks, then markers to see if your coin is from the same die listed. But there are many die states and things happen to the dies with age, even trading out of reverse/obverse dies may happen and the markers will be new for the replacement die. Markers help, but only after you figured out the Separation, then Location first. Just too many Cents out there with the marker die crack/break on column # 12 to match to a certain die. So look of the separation and locations first.

And to add to the above, there are many dies that will leave markers, but will not be the same die in a given case, Particularily, if it is dated before 1989, and has a MM. The MM having been "hand-placed, or punched, will end up being one if not the final determining factor(s). If I am in error, in any part, please correct me. I'm learning, but still a "newbie".
Dick

I'm guessing more of the hubbing issue, not the hub. The process on the single squeeze seems to be at fault. Some refer to it as snap back into the right position as it didn't hit correctly or in some cases a re-hubbing after the operator could see it wasn't in proper alignment. On the multiple hubbed dies, hub wear or using a different hub or rotation/movement of the hub creates a separate spread image on the die. The same hub may make the non-separated dies as well. But the hub is somehow changed/worn/not in the same alignment when hubbed the second/third hubbing. So the doubled/triple die is created.

Die varieties are not the result of faulty hubs, rather a fault in how the hub met the die. If the die is not set correctly in the press when the design is placed into it, the result can be a doubled design on the die, thus a doubled die. The doubling is called "hub doubling".

Repunched mintmarks are a thing of bygone days (pre 1990) when mintmarks were placed into the individual dies by hand. If the punch wasn't sitting right or if it had to be punched in deeper after the initial punching, any misalignment would cause doubling of the mintmark - thus a repunched mintmark.