Chuck Harris wrote:

: The part I find odd is usually when RCA is listing a similar tube
: they will say something like plate curves match 6L6, or some such.
: There is a total absence of mention of the 829B in the 3E29 spec
: sheet.

Oddly, after all my previous post, I hadn't looked at an RCA 3E29 spec.
This old one (TT?) from 1946, does say " Similiar to type 829-B, but
intended particularly for pulse modulator service."
http://www.mif.pg.gda.pl/homepages/f...049/3/3E29.pdf

Still unclear on what makes the difference, though.