The small roundel was standard on pre73 ( roundy )
no trunk badge before 74
Here's from Bavarian Autosport (NH)
(click to see more) Trunk Badge - on rear panel
Part # : 51 14 1 801 560
It need two grommets. ( horizontal )
For the diametre ??
I will have access this wk end to 2002
should have the answer.