I recently got a 50/3.5 Minolta Celtic macro lens from an eBay seller. From the photos and description it just looked like the lens needed new focusing ring rubber. Sometimes that look alone will really bring down the price of a lens. When it arrived I didn't examine it too carefully but left it with my repairman. It turned out that the lens elements had fungus in and/or on them and it looked like it would be difficult to clean it up. I already had a number of these and other 50/3.5 Minolta manual focus macro lenses so I didn't think about it too much. Then I remembered that that another eBay seller kept showing a 50/3.5 MD Rokkor-X which looked like it had been dropped. I got it for $17 and packed up both lenses to send to my repairman. I am hoping he will be able to replace the bad elements in the Celtic lens with the good ones in the MD Rokkor-X. As far as I know the formula for this lens did not change between the time it was first offered in Leica 39mm and Minolta SR mounts as a pre-set model. The coatings certainly changed over time. The Celtic uses the metal barrel construction of the Rokkor which was made at the same time. The MD Rokkor-X has the same plastic inner barrel construction as the late MC Rokkor-X and later plain MD models so it may take some doing for this to all work out. If it doesn't then I will look for an MC Rokkor-X or MD Rokkor-X or MD in good mechanical condition but with bad glass. It is rare to find a lens like this with front element problems like scratches because it is recessed so much but the rear element is another story.