[Amps] Anyone ever use a 6C21?

[R.Measures]

>Mark:
>
>I built an AM "transmitter" using a pair of 6C21in push-pull several years
>ago.
>
>The tube is very much the same as the 450.  Eimac specs call for 8.3 volt
>filament voltage, but that was for pulse service.
>
>They work just fine in class C with 7.5 volts.  Several times I interchanged
>the 6C21s with 450s and saw very little difference in anthing measurable:
>power out, plate current, grid current.
>
>I doubt they would be suitable for linear service.

***  A triode with a Mu of 38 is OK for linear service, but only in g-g 
configuration, However, the drive requirement would be higher than it 
would be for high-Mu tubes.