In the Fonts control panel, it just says "System Font", but this is not SF Display Pro
>(OSX 4.6)
?
> the "a" is certainly different.
Still SF. See https://forums.developer.apple.com/thread/79047
What is the typeface used in Notes app for OSX & iOS?
SF comes in display and text versions. Notes uses system font, so if it's not one, it's the other.
Assumes you meant macOS vs. older OS X.
Can I ask why you ask?