I wanna throw out die polishing lines cause out of all I’ve seen on shields they are a lot more aggressive and sharper looking then these also thinner. These are mor soft looking. Also not seen in a perfectly circular way like these. A few aren’t perfect tho. These are pretty uniform for the most part even spaced etc. lathe lines kinda 5/10.
They might have used a Dremel while attending Drexel, but using a Drexel might have produced differing results
They do not look concentric enough to be Lathe Lines, I think they are die cleaning lines. Most likely made with a circular die grinder with an abrasive pad on it. JMO.
I wanna post it on CCF but it won’t let me size the image to the requirements needed for some reason at all
whatever software you are using to look at the image, or others, look for an "export" where you can change the resolution for a smaller file.
Based on your observation, one can definitely conclude that these are not lathe lines. What is more likely is that a more flexible abrasive medium was used on the face of the die after sinking it, and not before.
Zooming the image, the larger rings seem to consist of tiny bubbles themselves: Is it possible we're looking at some sort of concentric ring plating blisters instead of the more common linear blistering on zinc Lincolns? I can find no equivalent image of circles from web searches, but the linear plating blisters example on error-ref shows similar characteristics (made of multiple tiny bubbles): from https://www.error-ref.com/blisteredplating/ specifically: https://www.error-ref.com/wp-content/uploads/2013/12/55041234.jpg
I think your coin shows die polish lines Lathe rings are concentric. The marks on your coin, show variable spacing and direction. Compare yours to the pic from errors-ref below Concentric lathe rings from error-ref
