I've searched far and wide for a way to remove this sort of brake lever but I have not had much luck. Attached is a picture of the lever, apologies for the quality. It's an 80s Shimano 600 lever, secured by a nut screwed on to a bolt going through the pivot mechanism. How do I go about removing this? I've tried long-nose pliers but can't seem to get the nut to turn. My smallest crescent wrench--which is fairly small--doesn't fit. All other levers I've worked with up to this point have been secured by a simple allen bolt. Any help is appreciated.