5cm Summicron distance scale

[raid]

I have three rigid Summicron lenses in 50mm focal length. They are Made in Germany in chrome. Two are regular Summicron lenses and one is a DR for close-focus. I still have not bought the finder for it,

One of my Summicrons has distances marked in feet (later serial number-1958) while the other has distances marked in meters (earlier-1957).

Do you know of the specific range of serial numbers for distances marked in meters versus feet? Has the coating color/type changed for the Rigid Summicron at some time?

 

[analoged]

Lenses were marked for country of export, i.e. USA would be in feet, not by serial numbers.

 

[raid]

This makes sense. Thanks. This is maybe my favorite lens.