need help finding the minimum aperture for an old lens

[aj-images]

Hello - Hoping to find out if anyone knows the minimum aperture for an old Rodenstock-Tiefenbildner Imagon lens, # 3587796. There are no f-stops on the lens. Shutter speeds are 50,25,10,5,2,1. Any help would be appreciated.
-Jim

 

[aj-images]

This is a 300mm lens.

 

[jonw]

try this link, I think it will answer you question or at least shed more light:
http://66.102.7.104/custom?q=cache:...denstock-Tiefenbildner+Imagon+&hl=en&ie=UTF-8

 

[aj-images]

Thanks for the link, that helped a lot. - Jim