Difference between US QWERTY and International QWERTY Apple keyboards? What exactly is the difference between US QWERTY and International QWERTY Apple keyboards?

I’m talking about the hardware keyboards specifically, not about keyboard layouts (in System Settings).
The most important differences are the size and position of the Enter/Return, and a few differences in the layout. The ~ key and the \ key have an entirely different position on both keyboards. Also, the US keyboard has no € label (although it can be entered: Alt+Shift+2). 

The International keyboard (‘keyboard type’ = ISO) also has one more key than the US keyboard (‘keyboard type’ = ANSI).  Some Apple keyboard layouts use that key for essential characters, and this can cause problems for users with only the US keyboard.

Below is a high-quality visual comparison.

US QWERTY Apple keyboard:



EN International Apple keyboard: