[Milsurplus] Friction tuning drive wanted

[Military1944 at aol.com]

Friction tuning drive  wanted        
 
I am in need of a friction tuning drive. This is the type with  a larger 
centre knob and a small knob off to the side that rotates the bigger  wheel 
buy means of a friction wheel between the two. The centre knob has a white  
outer rim, 2.75 inch dia, with 0-180 marked on it. The is a second ring under  
the white one which is the friction wheel that the smaller knob drives. 
 
If anyone such a drive I would interested in buying it. if  uncertain I can 
send a picture of the actual thing needed. 
 
Many thanks, Ben.