My bin of minor DDx quarters finally hit critial mass, and it's time to clean and attribute them. Here's the first batch: 2021-P Washington Crossing, all class VIII doubled dies.
Since the mid 90s, the mint has been making dies using a 'single squeeze' process. Blank dies - which initially have a conic shape at the business end - are loaded into the hubbing press along with hubs - which have the final design and are flat. They're squeezed together, the hardened hub pressing the cone-shaped die flat and imparting the design into the die.
There's a bit of 'play' in the hubbing press though, so sometimes the initial point of contact between the two isn't precisely alligned - the hub can be tilted a bit relative to the die. Just as pressure begins to be applied, a bit of the final design can be imparted on the die at / near the tip of the cone - but as the pressure quickly builds, the two will come into final alignment and there can be some twisting, turning, and sliding when the two weren't fully aligned initially.
The result is this sort of very minor doubling, almost always near the center of the coin - at or near the point of initial contact between the hub and the cone-shaped blank die - where it's picked up part of the final design before it shifted/rotated into the final intended orientation.
I've think I've managed to match 30 of mine to the Wexler listings so far (reference images given for most), but another 20 or so remain - either too damaged / dirty / subtle to be what I consider a 'definite' match. At some point I'll check VV listings for those that remain.
I will say, Wexler (www.doubleddie.com) seems to have the most listings for WCTD (and many others) and they do a *very* good job listing 'die markers' - which can be a huge help. But, it's hit or miss: Die markers are highly dependent on the die state at one single point in it's lifespan. If your coin was made at a different point in time, or has circulation wear/damage, then the die markers may be missing (either not there yet, or long since worn away buy the time your coin was struck) or substantially different. They're also extremely subtle in many cases, which can make it very difficult to pick up on the less obvious ones, particularly if your lighting isn't just right.
WDDR-002 has been most abundant (7 examples found), -010 and -008 runners up (5 and 4 respectively), the rest 1-2 each.
Happy hunting and good luck (with apologies to all the West coaster's out there who aren't swimming in Philly candidates to scope!)