The 807 and the 1625 were identical except for the 12.6 Volt heater of
the latter, and its 7-pin base as opposed to 6.3V and 5 pins for the 807.
The 6BG6 was the same as the 807 except it had an octal base.
 
There were so many variations of the same cathode-grid-plate structure
that it's hard to keep track of them all.  There were tubes like the
7581, 5881, 8147 (not sure of that one), 7027-A, even the EL34 was
close.  There was an English tube the KT34, too.  Gads, the list is
awesome, and frankly they all did just about the same thing with minor
differences in ratings, shape, maximum frequency, and so on.  I used a
5894 in a mobile rig back in 1957; I think I was the first ham to use a
transistor power supply in a mobile rig.  I used a pair of Delco
2N174s with a home wound toroid saturating transformer.  Worked Korea
with that thing, about 10 Watts, 10 meter AM.  Great fun!
 
73 DE K6DDX
--- Maximus 3.00
---------------