Which manufacturer specified 100 W at 700 V for 2x EL34 ?
For instance Telefunken specified in 1964 "Special quality" section
100 W at 800 V and max Ik =150 mA.The only time I have seen 100 W with 2xEL34 is in one Marshall base guitar amplifier. In this amplifier the Philips/Mullard tubes literally melted after a few hours, the Telefunken tubes were the only that survived.
Typically a normal 100 W guitar amplifier had four or six EL34 tubes at slightly above +400 V anode voltage.