Dynatron T99 Tuner

[Excessive Leakage]

It appears that the US equivalent is the 6AE8, http://www.radiomuseum.org/tubes/tube_6ae8.html , which is also an elusive valve.

The following may be of interest if you struggle to find the X79 http://antiqradio.com/post_6ae8-replacement.html

Cheers

Adam