David Clark Comm Cord Kit for H10-21 Headset – 18028G-56 Garmin VIRB and external utility slot

and external utility slot

Here's more information straight from the manufacturer:

Description 12 X 18 VINTAGE METAL SIGN - FANTASY VINTAGE

or fleet servicing

David Clark Comm Cord Kit for H10-21 Headset – 18028G-56 Garmin VIRB and external utility slotDavid Clark Comm Cord Kit H10 21 Compatible Ensure reliable communication with the Original David Clark Comm Cord Kit, designed specifically for the H10 21 headset model. OEM Approved Replacement: Genuine David Clark part (P N: 18028G 56) ensures full compatibility and performance. Model Specific Design: Engineered to fit the H10 21 headset. Durable Construction: Built with high quality materials for dependable, long term use in aviation environments.