The EBC90 is an amplifier triode with double diodes sharing the same cathode. The EBC90 was designed for use in superhet receivers.
Seen in profile the two diodes are the outer structures while the triode is housed in the central dark anode. The central cathode tube is oxide coated within the triode and then a second patch of coating has been applied to the part that extends within the twin side anodes.
The central cathode showing the oxide coating to provide emission for the two diodes.
The diode anodes have a pressed groove in them to stiffen the thin nickel sheet. The wire rectangle in the foreground is the getter holder.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 48 mm tall.
References: Datasheet, 3002 & 1040. Type EBC90 was first introduced in 1953.