This is a FIDENZA 6310 in clear glass, 3 shell, rated @ 10KV.

The embossing is very strong and the condition is excellent.

I do not think there is a CD number assigned to the FIDENZA 6310 but the insulator is very similar to the FIDENZA N 10B which is assigned CD 375. The FIDENZA 6310 may end up a CD 375.X