1938 proof nickel DDO DDR cover up Conspiracy theory
Aspie_Rocco
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Preface: i am not an expert by any scholastic standards. I just spend unusual amounts of time studying images of coins and actual coins.
Also. Brain not braiding well today. I'll edit out the incoherent stuff later.
Body
I believe many or most of the Proof Die for nickels in 1938 are DDO and or DDR.
I believe the re engraving on the ribbons, letters, and numbers of most dies is covered up spilt serifs. 
The FS 402 version is unoutched on alphanumeric points, on the obverse. Only the Ribbon is enhanced. This may by the only non doubled ?
The reverse of all 38 and many years following has re engraved details on proof and business strikes which I believe comes from the original master dies or what ever it's called.
I will present photographic evidence of my theory when I have more time and my brain is functioning better. 
Comments
401 additional serif on S of Trust and re engraved alphanumeric details
402
Ribbon only enhanced. No obverse alphanumeric touch ups
403 enhancements to ribbon and alphanumeric points
https://www.autismforums.com/media/albums/acrylic-colors-by-rocco.291/
It could be - what about the DDR, is there re-engraving there as well?
There are as many minor variants of 1936-42 proofs as there were new die-polish-repolish events. Some dies were repolished multiple times and retouched each time. [Check the new book United States Proof Coins 1936-1942 for additional information.]
(Don't know what to make of the "cover up conspiracy theory" comment. No indication of anything like that.)
By cover up I reference the re engraved numerals and letters on both obverse and reverse of most issues.
I think they tried to engrave over the doubling.
Every re engraved 38 proof I have seen, except the 402 version, has apparent minor doubling under the re engraved parts.
Conspiracy is way to strong a word to use, but I couldn't think of a similar word to express it.
https://www.autismforums.com/media/albums/acrylic-colors-by-rocco.291/
Interesting correlation Aspie_Rocco; on many occasions I wished to have such an eye for detail. Hope you uncover something- you have my vote of confidence!
Ah... You mean trying to repair or cover some prior die defect? Now I understand; and there was no "conspiracy."
Nice detail examination and photos.
Oh, do you mean like the 1958 Lincoln ddo? It got knocked down from ddo as being simply engraved again.
Due to the hardness of the metal used, there have been instances of 'bifurcation' on the ends of letters and devices on Jefferson nickels. It matters little with business struck coins, because a nickel is a nickel and billions enter circulation. For collector coins however, the proofs are scrutinized a bit more. The anomaly happens on the working dies so any minute doubling (split seriffs) can occur without rhyme or reason, so in this instance, it's not a true doubled die. Keep searching, keep posting, just throwing this out there for digestion.
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