Have A-Series knob, (case secured with cotter pins, latch interlocks with lock body, screws are concealed) about 30 years old, will only take a 5-pin cylinder, identical to one out of an old F-series knob about 20 years old. (I know it's F-series since screws are exposed, latch looks much like Kwikset, knob has flat spindle that goes through latch.) First, other posters here state that F locks are supposed to have pot-metal cores, but this one has a normal brass cylinder with screw-on retainer. Secondly, I thought A-series was supposed to take
6-pin cylinders, but on this one there is no room in the knob (brushed aluminum finish, tulip style)for the 6-pin What is going on?