I believe the early ones were designed so that the slotted screw which secured the handle could be adjusted with a coin, prior to starting fishing (rather than while fighting a fish). Is it possible that the original slotted handle nut was replaced with the brass-like one your reel has? And does loosening your handle nut change the drag?
The brake setting is preset by ABU and cannot be changed like for example, the Abumatic 120 can be changed with a slotted screw.
The braking effect can be influenced by releasing the crank during the drill (auto-syncro-brake).