Standard SDC2300 headphones.
These are the Koss UR30 headphones with the special connector to suit the SDC2300 detector.
This is a genuine Minelab spare part.
Booster - Booty Mk1
Booster - Booty Mk2 with bypass
Headphones - CTX3030 Waterproof Koss
Headphones - GOLD MONSTER 1000