"Gong played on Rim"

Yup,

So does this mean on the narrow edge of the gong? Or simply towards the outside (generally black-coloured) area?

Anyone know where I can hear the difference?

Hitting the edge of the gong would be difficult, as the frame that holds the instrument up would get in the way. Why bother?

Hitting the edge of the gong would be difficult, as the frame that holds the instrument up would get in the way. Why bother?

Thats not entirely true and that sound is used in a number of pieces.

Yup,

So does this mean on the narrow edge of the gong? Or simply towards the outside (generally black-coloured) area?

Anyone know where I can hear the difference?

Honestly, playing it yourself is the only way. You could hear a recording, but generally such instruments sound much different, and therefore inaccurate to your intentions, on recordings.