I've been using a collapsible Summicron for awhile, but I've found it to be very flare-prone. I went looking around for a rigid Summicron today, but I couldn't find a decent one for a good price.
Most of the lenses I looked at were either beat up or scratched up, and after awhile I gave up looking. As I was walking home, I stopped by a small used gear shop I know, and they had a mint DR Summicron with it's set of eyes. I've never seen such a clean lens unless it was still in it's original box. I couldn't find a mark on the glass or metal, and the price was lower than what I had seen a couple of the battered lenses selling for, so I grabbed it.
I attached it to my M4 as soon as I left the shop, and shot a couple of rolls of film. I'll shoot a couple more rolls tomorrow and develop the lot on Tuesday, I'm looking forward to seeing how well this lens performs.