You're probably right, maw, that I should have had a better look at it on arrival! I actually got it just as I started having some eye issues that took a string of surgeries to resolve, so it hasn't gotten nearly enough use. Though my experience with it has for the images I have captured been overwhelmingly positive... as Hans is saying was the case for him, I don't feel I've run up against IQ problems.
Still, you aren't wrong to be worried: with a very bright light reflecting the right way though I do believe contrast would be severely affected.. managed to hit this angle... not quite perpendicular to the optical path, when the dust becomes much harder to see, but not too far off either...