Can someone tell me if they have ever seen a primary lens with several perfect concentric circles in the centre of the front lens? The circles cover about a 10mm in diameter

My Vixen 102m has these markings. They are very faint and look as though they are part of the coating or an integral part of the lens.

They are not easy to see and I don`t think they are on the surface. More like in the coating. The scope gives excellent views and as far as I can see, good refraction patterns in and out of focus. so could this be a coating fault?

Many thanks, Bob