I have the new version R-28mm f2.8 ROM. I bought it in mint condition, though used, and very carefully checked that the glass was perfect. That was about a year ago. Yesterday on a job I noticed quite a lot of cleaning marks on the front and even rear elements, and I'm rather perplexed. <p> First, I don't clean the lenses very often, I have probably cleaned that one about four times in more than a year. When I do that I use a good cleaning solution with the kodak papers. The first thing I do is with the first tissue, saturate it with the cleaning solution and gently mop up anything on the element, namely dust or whatever. I usually do that twice to be sure all the dust is off--using pretty much no pressure. Then I take a couple dry tissues and slowly work off the solution. <p> Now, under a loupe, there are cleaning marks ALL OVER the front and rear elements. However on my R-35mm f2.0, which I have cleaned much more and is about 20 years old (also bought second hand) has almost no evidence of cleaning. <p> What is up with this? I thought the Leica coatings were supposed to be super-tough. I have really babied my glass and I'm rather ticked about it.