1959, 263g, 8 iris blades, MFD = 0.5m, $27 @2018
AR I due to F-stop to 22, blades are a bit oily 61 yrs old
and also missing tiny screws to hold the metal focus ring
(fixed two missing screws using parts from old lenses)

There're half stops between F2 and 5.6, although you
have to press the lug(→) to rotate the aperture ring.
This lug is the same as Auto Rokkor-PF 55mmF/1.8's.