How to test a vf14 tube

[anjing]

A friend of mine has an old u47 with telefunken badge. The mic is in bad condition. The inside is all rusted. I'm looking for a way to test if the vf14 tube is still usable. I was wondering if anyone have advice on how to test it. I have limited internet access so i tough i would ask here.
Thanks in advance!

Pierre

 

[micaddict]

Just for some inspiration:
http://www.gearslutz.com/board/high-end/804173-u47-before-after.html

 

[anjing]

Thanks mic addict.