My lever, ex Drags, is slotted but has a round hole on the top side to part way through. The slot only exists for perhaps a third of the total length of the hole, as per the originals. I assume the slot going only part of the way through is for ease of manufacture but I suppose it could also be to allow a small amount of rotation before the brake rod has to bend if the joint between pin and arm becomes solid.
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.