AC Adapter Barrel Jack 5.5mm 2.1mm From Speakers 9V 300mA (CT9)

Working a few years ago.
It came with the speakers of the first PC I bought back in 1998.
I kept them for testing use until one of them died a few years ago.

The barrel jack is 5.5mm outer and 2.1mm inner. Output 9v 300mA.