808 transmitter triode

This is an old US-made (General Electronics Inc.) transmitter triode from WW2-times.

The Anode is rated for 50 Watts of maximum dissipation. Heater ratings with 7.5 V, 4 A are considerably high for this relatively low-power tube. When heating this tube, it lights up bright like an incandescent bulb. I assume, it still has a pure tungsten filament thats needs to be heated up to 2700 °C for sufficient emission. Grid connection is at the side cap, the base supporting the filament leads only.

At the base of the bulb, there is a small Barium flash getter.

Some things I don't understand of so far:

First - what substance(s) is the anode made of? It cannot be pure graphite, since the plate is very thin - just like being made of tin. But it looks like being sintered or pressed from some granular substance. And - what's most interesting - the top wire connecting it to the cap - seems in some way to be soldered to the plate cylinder - the soldering metal - must be a very heat resistant one - can clearly be seen when looking from above.

Second: The triangular porcelain grid support plate, fixed at the filament leads, has at its upper side some metallic looking coating - an integrated grid leak resistor? But with my mulitmeter, I only could measure an infinite resistance between grid and filament. What is it for?