The grenade in this episode is a Mk 2 hand grenade. Developed in 1918 and widely used in World War II, it is made of cast iron with a grooved surface divided into 40 knobs in 5 rows of 8 columns. This was intended to enhance fragmentation. It has a 4-5 second fuze before detonating.
The label on the record reads SYMPHONY TO A FACELESS STRANGER.