Can someone tell me what is being referred to when the term "gray halo" is used? I read this in the context of a Speedmaster 3572.50 and the actual comment was: "The correct wording on the case back and the absence of the "gray halo" are major pluses in my view"

Cheers

 

It's the grayish circle around the dial made by the sapphire crystal - look at my profile pic for an example

 

Thank you, kindly.