The 'C' is "Not" a bayonet 'N'.? It is much more like a giant BNC, with a much greater total distance between inner and outer contacts than any N type.? (Within the mating parts at least.)?
Plus the contact surface area is much more generous than many others of the same overall outside dimensions.
But like the BNC, it's mechanical stability & longevity is poor.
I know as I've had to replace too many of them.
They were popular for valve(tube) linear Anode(plate) DC power interconnects a while back.
