Hi Smith and Welcome to the board...

Have you tried to take a photo of the base directly under/close to a strong light, and take a pic. Sometimes the camera pics up more than our eyes do -- and sometimes the light at close range WILL show some marks as the light shine through the glaze. ...and sometimes the camera picks it up better than our eyes ( no flash either)
Try that to see IF any mark might show through first --
process of elimination...Again Welcome to the Board