It’s a strange and quirky arrangement ! In 1927, the drive ‘thingy’ for want of a better word, was advertised as being made out of “Pen Nib Steel” !! Presumably strong spring steel, but to describe it like that was very odd. I have the B & L Mk2 pump, with the ‘tell-tale’ plunger to confirm when it is working, the special crankcase door, and the long, cranked door strap that holds it all in place, and the bit of ‘pen nib steel’. I don’t want to sell it piecemeal but would consider selling the lot. No idea what it is all worth though !