While the Summicron and Rokkor 90mm f/4 lenses were identical and made by Leitz, this is not true of the 40mm. So as far as I know it's not quite right to call it a Summicron. At this stage the CV 40 Nokton is a better lens: it's faster, it has equal or (in many opinions including mine) better IQ to the Rokkor, and as it's much younger, it's far less likely to develop haze or fungus in the next 15 years.