Master Die Doubling Question

Is there a specific denomination you have in mind?

Probably the best way is to read the more esoteric analyses on sites like Wexler and CONECA. Even then, those experts are making an educated guess on whether something represents master die doubling with multiple master dies in service, versus working hub doubling. I imagine that part of the analysis would be whether the same doubling appears across multiple years, but not consistently across the mintage.

Thanks for the suggestion! I have combed the usual resources and asked the question in multiple places, but have not found an answer!

The existence of MDD might suggest that a Master Hub was involved - or does it? We know that, in the past, there have been instances of Master Hub Doubling created by the movement of the stylus needle on a pantograph machine. Is a similar even possible from the stylus on a CNC machine? I have found no discussion of that question.

I am finding a couple of attributed examples in the time period of my interest - after 2003:

2022-P 25¢ MA WMDO-001 & 2022-P 25¢ MA WMDR-001
https://www.doubleddie.com/2680879.html?
Description: Doubling to the north on the last T in TRUST and the first 2 in the date. Slight doubling to the south inside the nostril.
Description: Very slight doubling to the east on Angelou's ear and the rightmost letters of MAYA ANGELOU.
"WMDO-001 is known on 2022-P Angelou, Ride, Mankiller, and Wong quarters. It is expected, but unconfirmed, on Otero-Warren quarters. Most, if not all, of Angelou and Ride quarters show this master die doubling. It is less common on Mankiller and Wong."



2023 Doubled Master Die
https://www2.briansvarietycoins.com...gs/view/1869?

For the nickel, Wiles has a Doubled Working Hub that is similar in 2022
http://varietyvista.com/04d%20JN%20...2PDDR001.htm

But if those numbers do no include ALL, and there is no obvious reason that the doubled feature is not present, how does that translate to MDD?

The goal of the mint is to average 500,000 strikes per die. One die lasts a day to a day and a half. A large number of dies are used to strike one issue. One issue will be produced on at least 3 to 5 presses at the targeted rate of 750 coins per minute. How do we quantify "sheer numbers" - - if not 100% of the 50 to 100 coins examined, how can we say Master Die Doubling?

Pete, you will find these things can and will change over time. Their first thought in these situations are a doubled working hub, but as more examples come along and less "normal" examples are seen, their thought process can change. You see many of the doubled dies become delisted over time, as they have more examples (too many) to be just a doubled die. I feel the same happens with what was thought to be a doubled working hub is actually a doubled master.

It is indeed reported that the Mint is using CNC master dies.

This is exactly the issue behind my questions: With CNC Master Die production, there is no need for a Master Hub - - unless that they are being used in parallel and Master Dies are being produced by both methods?

I can cite references for both =
1. Master Dies are used to initiate die making
2. Master Hubs are used to initiate die making

I am at the point where I have a growing suspicion that sources asserting the continued use of Master Hubs are simply relying on "Mint lore" for the die making story without verifying that the story is currently in practice!

By exploring Master Die Doubling after 2003 (2004 the Mint was first involved with CNC) I am attempting to see if that can be pinned down any more precisely.

The short answer is yes. I believe master hubs are made on a micro milling machine. As such, the tooling used would be end mills - probably tapered ball end mills for the details. Due to tooling diameter, there is is always a chance deflection. Many things affect deflection of tooling. Also, given that the table moves and not the tool, the table must move from the same direction to prevent a slight in accuracy in location. For instance, if the table is moving to the left and you interrupt the cut, you cannot pick up the cut with the table moving to the right. There will be a mismatch however small. All moving parts have some degree of play.

Everything I have read is suggesting one or both (when it comes to a master hub or just master die), so I have no good answer. The best I can tell though, it is all digital, regardless of it starting with a master hub or master die. Another murky and grey area with the U.S. mint and their processes.