I was just in Genius bar and the guy said that if I boot into my external OS, that drive will be at top of the desktop. I have never heard or seen this, and just tested and in fact the Mac HD remains at the top. So it appears he was wrong. and he was smart.
The old way I know is to go into startup disc, and see there.
Now, I just did that while I was booted into the backup external, the Mac HD was selected, is that correct? the one you are NOT in is selected?
Is there another quick easy, intuitive way to know which disc you are on?