So I have checked the item: it works well and the glass does not seem to have any scratch, but I was surprised to see that the "few dust" you mention in the "Photosystem" are indeed within the optics... I didn't think it was even possible.
In the tests I have done I haven't been able to see any effect yet, I just hope it will not show up at a bad time.
Anyway the item is as advertised and I keep it, thank you !