The H210 is a dull emitter triode from Tungsram. It was designed for use as an RF or detector valve. We also have the metalised version of the H210.
The Top etching gives the details of the valve. The top lettering reads made in Hungary.
The box anode is angled within the balloon envelope. The filament is made of very fine wire and is formed into a single V within the anode. In the full sized picture the filament can be seen and is held in the supports that are folded over to clamp the wire. The blackening of the envelope at either end of the anode suggests an Azide process valve. And the envelope letting confirms it as a barium tube.
The balloon envelope is 47 mm in diameter, and excluding the B4 base pins is 92 mm tall.
Reference: 1043. Type H210 was first introduced in 1929.