Which way for the ground glass for a Bergheil?

Due to the ground glass for my Voigtländer Bergheil 6.5x9 being extremely dim despite me trying to clean it when in the holder I took it out and gave it a real rinse in the sink. Wow, I gained at least one stop and clearer focus!

Dumb as I am I didn't check which way it should sit in holder. I put it in with the matte side towards the camera as it felt logical, but can somebody give me feedback on it?

APUGuser19 said:

dull side towards lens, always.

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Wonderful answer there! It would be highly illogical the other way around but I just wanted to be sure.