Take a small flashlight with you. The more powerful the better. Shine it through the lens to detect any haze. This isn't really applicable to a lens as recently built as a Contax G lens, but may be useful.
“Believe nothing, no matter where you read it or who has said it, not even if I have said it, unless it agrees with your own reason and your own common sense.” – quote
I myself am made entirely of faults, stitched together with good intentions. -quote