I am looking at a used Caltar II-N 360/6.8 serial number 10624 261 and the selle r does not know its age. It looks like this is a Rodenstock APO Sironar N 360/6. 8. I called Calumet and they said that if it is under 7 years old then it is the APO Sironar N. Can anyone help identify this lens?

Thanks, Peter Shier