Great looking mold... I love brass molds. I only have one, so far, for my Whelen, but good grief, they are pretty... and cast good bullets.
I've had that happen to my molds, also. I don't have a clue where it comes from, because, as mentioned the only time you could get splatters on it was when it was open.
I use either a dental pick or the tip of a scalpel/exacto blade, and HIGH magnification to gently pick spots off the face, and chase the vent lines if needed. If you leave the spatters there, it will only get worse (somehow
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