This double diode appears to have a cylindrical anode, but in fact the visible cylinder is a screen strapped internally to the cathode. Within the screen are two small anodes mounted vertically around the cathode.
The classic envelope is 37 mm in diameter and, excluding the B5 base pins, is 90 mm tall.
References: Datasheet & 1043. Type 10D1 was first introduced in 1936.