Like many classic fonts, there are several different cuts of Gill Sans by various publishers. Monotype distribute it as 'Gill Sans MT', and Adobe and ITC have their own versions.
Which version is the version that is distributed on a Mac? I can't find any authoritative answer or clues in the font files themselves. All I'm able to discern for certain is that Gill Sans (Mac) and Gill Sans MT aren't identical - at regular weight, they're almost identical (tiny, tiny differences in aliasing but no significant differences), but Gill Sans Bold as bundled with a Mac and in MT version are simply very different weights. (I currently don't have access to Gill Sans Light to test).
So, which cut of Gill Sans is it that comes with Mac OSX?
For bonus points, if it's the Monotype cut:
- What are the weights of the "bold"s and "light"s in Gill Sans and Gill Sans MT? On the bold side, it looks like there's a difference of at least 200
- If it's possible to complete the Mac Gill Sans set so that it matches the Gill Sans MT set by buying and installing the missing weights, is there a way of changing the namespacing so that a file created using the Gill Sans MT set imports correctly using the same-weight equivalents from the Mac set without needing to replace fonts each time?