The folder where macOS stores the icons it uses at the system level is
/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources
That's where you'll find it.
The contents are pretty cute, so here's a quick look inside.
Roughly speaking, it looks like this...
Inside, you can find icons for nostalgic Apple products that are no longer sold.
There's even an icon for the Apple Xserve, the rack-mount server sold for industrial use from 2002 to 2011...
Cute little monochrome icons
The black MacBook https://pc.watch.impress.co.jp/docs/2006/0523/apple.htm — I learned it existed from PC Watch, but I've never actually seen one in person.
Some icons disappear with OS updates, so it's fun to check back in on this folder every once in a while.