Adrians free time projects
The PC900 triode is a high mu / high gm semi-remote cutoff triode intended for RF circuits, including automated gain control if the signal range to be covered is less than 3 decades.
Note that this tube shows gm drift (about -10%) when the plate losses are small (say less than 1 watt). In that case, my "cold" measured PC900.i5 model might be more accurate.