MacOS – “More info” button missing in “About this Mac”

Most of the difference you're seeing is due to Time Machine's "Local Snapshots" feature. When Time Machine is turned on but the backup device isn't available, it backs up to the local volume. The space used for these local snapshots is counted as "in use" by Disk Utility and System Information, but not the Finder (see the Disk Space considerations section of this article). While the space for backup actually is in use, it'll be freed automatically when needed (i.e. when the volume gets above 80% full), so the Finder counts it as being available.

In your particular case, the space System Information lists as being used for "Backups", 98.36GB, is very close to the difference in free space listed by the Finder vs. the other two. The Finder's 206.43GB free - 98.36GB of backups = 108.07GB actually free; compare to System Info's listing of 108.44GB free and Disk Util's 108.31GB. I'm not sure what the rest of the difference is (maybe they looked at the disk at slightly different times? Or they may be counting volume structures a bit differently?), but it's very small.

Finder shows:

• easily, the truth for JHFS+ volume Macintosh HD
• optionally, the truth for mtmfs volume MobileBackups

Hint: with local snapshots enabled in Time Machine, in Finder you can go to /Volumes/MobileBackups then get info.

Results of a one-line command show that for some purposes, MobileBackups is treated as a distant file system:

qlmanage -m disks | grep MobileBackups && mount | grep MobileBackups

As Disk Utility is oriented to local file systems, we'll probably never see MobileBackups as a separate volume in that context. There are degrees of simplification in Disk Utility, even when debug options are chosen.

You can indirectly get this information from a web page and the curl command. In the past this URL has been taken down and rate limited and put behind some sort of captcha to prevent this use, so you might need to resort to other avenues like https://checkcoverage.apple.com/ in that case.

Depending on if your serial numer is 11 or 12 characters long take the last 3 or 4 characters, respectively, and feed that to the following URL after the ?cc=XXXX part. If your serial number was 12 character and ended in DJWR, you would issue this command:

curl https://support-sp.apple.com/sp/product?cc=DJWR

To get your serial number, use the following command:

system_profiler SPHardwareDataType | awk '/Serial/ {print $4}'

Thus, you could have a complicated command to query the internet if you need a single command:

curl https://support-sp.apple.com/sp/product?cc=$(
  system_profiler SPHardwareDataType \
    | awk '/Serial/ {print $4}' \
    | cut -c 9-
)

and then run the output of that through sed to cut to the key part

curl -s https://support-sp.apple.com/sp/product?cc=$(
  system_profiler SPHardwareDataType \
    | awk '/Serial/ {print $4}' \
    | cut -c 9-
) | sed 's|.*<configCode>\(.*\)</configCode>.*|\1|'

There used to be a private library file with these mappings so you could consult it offline, but I noticed it was gone as of 10.8.3 (and perhaps earlier) so the above trick is the only one I know that works on the current OS without third party libraries.

Some nice third party libararies provide a look up of this:

• python code https://github.com/MagerValp/MacModelShelf
• JSON mapping https://github.com/krypted/swiftwarrantylookup/blob/master/src/swiftMacWarranty/model_snippets.json

Note that as of November 2017, Apple has forced the use of https over http for this service.