JianL
Established
Do the flashlight test and also shoot into the sun. I paid 600 Euros in March and mine is as clean as a whistle; not a hint of flare into the sun and like a new lens in a flashlight test.
At one point I thought it was soft at f/2 but that was my rubbish focusing; the USAF lens chart test says it's barely any softer at f/2 thah it is at f/4.
'clean as a whistle' are you sure? From my experience even brand new lenses purchased directly from authorised Leica dealers have dust inside (when a torch is shone through it). Can a decades year old lens really be cleaner than a new one?