B9D base
The 9-pin B9D (Magnoval) tube base is a larger variant of the B9A (Noval) miniature 9-pin base used for higher-powered tubes such as the 8608/EL5070.
See also
Links
Magnoval B9D base (IEC 67-I-36a) 9 pins with 1.27 mm diameter in a 17.45 mm pin circle diameter arc, e.g. EL503, EL509, PD500, etc. - not to be confused with...