[Amps] 4CX250B/F

[GGLL]

    Thanks for all the answers; the book I am talking is a re-print copy 
of RCA TT-20 manual (bought at RF Parts) which has specifications for 
power tubes. I think also (after reading the answers),  either was a 
print error or perhaps an engineer/marketing matter, also taking in care 
it's an indirectly heated tube. But in my ignorance the said difference 
popped up my curiosity.

Thanks again
Best regards
Guillermo - LU8EYW.