Hi all! Here's my latest conundrum. I'm restoring a Horseman 980 and would like to get any advice on what this smudge on the groundglass could be and if it's an easy fix or something I should take to the shop. As it is now the groundglass works alright although there is some perceived blurriness I believe due to this smudge. I think there are some sandwiches layers going on here and I've never taken a groundglass assembly like this apart. I'm crossing fingers and toes that this isn't something like mold or any permanent damage. Has anyone seen anything like this before? See photo:

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