Technically a Tudor bezel insert question but….

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I noticed on some of the vintage Tudor Subs the bezel insert seems to sink away from the bezel lip. Does anybody know why this happens? Did this happen on Rolex subs too? Can it be fixed or should it even be fixed?

Pics are taken from the web
 
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Any bezel insert aficionados? Does anybody know why the insert appears to roll inwards?
 
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They’re two different watches but I am tempted to purchase one of them. I’ve seen others like it and it’s really more of curiosity at this point for me