Is this 1953 D Washington Quarter Mint Mark an RPM or just Machine Doubling?

Doesn't look like anything listed so probably not impt.
Jim
When a man who is honestly mistaken hears the truth, he will either quit being mistaken or cease to be honest....Abraham Lincoln
Patriotism is supporting your country all the time, and your government when it deserves it.....Mark Twain
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My first thought is mechanical or strike doubling, because the way the right side of the D is a mirror outline on both “arcs”.
https://www.autismforums.com/media/albums/acrylic-colors-by-rocco.291/