The 1616 is a half wave rectifier designed for pulse applications. The peak current can be up to 2,500 mA and the design allows for a high peak inverse voltage of 5,500 Volts. Such demands would be placed on a rectifier that was required to recharge a capacitor stack after a pulse discharge such as that found in Radar transmitters.
The Westinghouse name on the base cap.
The Canadian Maple leaf logo and the letters REL and R within. REL stands for Research Enterprises Ltd. a Canadian Crown Corporation set-up during WWII and operated making radar equipment etc. for six years from 1941. This confirms that the 1616 was used within radar equipment.
The ceramic insulators are required because of the high voltages employed.
The classic envelope is 51 mm in diameter, and excluding the UX4 base pins is 144 mm tall.