Can you see the Newton Rings already on the photographic print or is it at first on the scanned result ? In that case it could possibly be Newton Rings from the contact between the print and the scanner glass. I know it sounds improbable as the print surface seldom is flat enough unless you ferrotype the print or use glossy RC-paper. It can be worth looking into.
I attached a picture to a post above where I've marked the rings in red.
"...the heart and mind are the true lens of the camera".
- Yousuf Karsh
"We are what we repeatedly do. Excellence, then, is not an act, but a habit".