The American Type 84 full wave rectifier is identical to the 6Z4.
The common cathode runs vertically through the two anodes that are stacked one upon the other. Each anode is identical and not symmetrical, thus allowing for the connections to be separated. Each anode is held by the support and a tab through the mica sheets.
The Brimar name together with the BVA reference and the fact that this American design was made in the UK.
The pressed anodes have a small central cavity for the cathode tube to pass through with only a small clearance.
The the anodes seen side view showing the relative diameters of the cathode tube and the anode cylindrical cavity.
The classic envelope is 37 mm in diameter and, excluding the UX5 base pins, is 89 mm tall.
References: Datasheet, 1040 & 1043. Type 84 was first introduced in 1937.