Classic Lightweights UK
Classic Components 

Campagnolo 'Open C'

Peter Underwood
The enigmatic 'open C' factor is a mystery to many.  To explain this subtle (a more diplomatic word than nerdish!) difference, here are examples of each, kindly photographed for us by Peter Lowry:

Campag Open C 1
Above: Lever with open 'C' Campagnolo
Below: Lever with closed 'C' Campagnolo
Campag Open C 2

Below:  Hub skewers showing open 'C' at top and closed 'C' at bottom
(Images Bob Johnson)
Campag Ooen C 3
Now we open another can of worms.  On the lower (newer) skewer cam-housing, 'BREV' is above 'CAMP', whereas with the top skewer it is not as easy to see that 'BREVCAMP' is in one line.  It seems that all 'Open C' skewers have this one-line stamping.  I wonder if this is a feature of the early Gran Sport to be changed on later models.