I recently bought two Nikon F55's on separate auctions each with a 70-300 and 28-80 and a bag coincidentally - I decided I could 'experiment' with one of the lenses I will never use ....[ both sets cost $50 each ]
There's the screw drive at the back ....
There's the cogs that connect the screw drive to the lens focus system ....
And the electronics ......
These contacts appear to relay the focal length to the lens pins
I still have some work to do to get it fully apart
.