Each tube itself is designed as a push-pull pair in a bottle :-). Spec sheet lists sub-2W class-A operation but I bet you could get a lot more power out if you parallel the sections and go to deep class C and ran the voltage way higher than the ratings.
Spec sheet at:
http://www.thermionic.info/misc/7699.pdfIn terms of RF power out of a single small bottle in class C... 5763 is probably still preferable.