Is the crystal on a 233 "softer" than other pams?

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I just saw my friends K series 233.. It had very light swirlies all over the domed crystal. I tried wiping it and used tooth paste to remove it, but its still there.they're not that pronounced nor can you feel them, but I accidentally noticed them when I was trying to photograph it with my phone and the led light went off.

The camera couldn't pick up the sfrathes, or swirlies, but I definitely can see them.

Comparing it to my 352, it was flawless. Well to be fair the 352 was newer.

But how did one get swirlies on a 2mm thick crystal? There were no visible deep scratches though..