Hmm... what a coincidence. I recently noticed a big piece of dust in a lens I bought from them "new " a few years ago. So just this afternoon, I brought it to a repairer to have it cleaned, and he told me that the lens has been taken apart before and is probably how that dust found it's way in there. I've never had it serviced before, so it would have to be that it was taken apart prior to my purchase. Now I don't know why it was taken apart before, the performance of the lens was fine, but I had to pay to have that dust cleaned out.