Mac OS 7.7

Mac OS 7.7 encompassed pre-release versions of the successor to Mac OS 7.6.1 that were renamed to Mac OS 8 (code named "Tempo").

Features
Some of the features from the cancelled Copland project, such as the Platinum appearance and multithreading in the Finder, were salvaged into Mac OS 7.7, giving it a different look and feel than previous versions.

History
Apple Computer initially planned the update as version 7.7. However, it was renumbered to "8" on March 8, 1997 to exploit a legal loophole and accomplish Steve Jobs's goal of terminating third-party manufacturers' licenses to System 7, effectively shutting down the Macintosh clone market.

Known pre-release builds

 * Mac OS 7.7 (d3), still identified as "Mac OS 7.6" with a partial implementation of the Platinum appearance.
 * Mac OS 7.7 (d4), codenamed "Spinal" with a more complete Platinum implementation.
 * Mac OS 7.7 (a2c5), codenamed "Speedy" with incomplete 68K support.
 * Mac OS 7.7 (a3c1), codenamed "StrikesBack".
 * NOTE: Subsequent alpha builds, starting with a4, were identified as "Mac OS 8".

Articles

 * The Heat on the Clones by Jean-Louis Gassée at Be Newsletter #63 (1997-03-05)
 * Apple Squeezes Mac Clones Out of the Market by Daniel Knight at Low End Mac (2014-01-25)
 * This Week in Apple History by Owen Linzmayer & Bryan Chaffin at the Mac Observer (2004-10-28)
 * Eight is Enough (and More Apple News) at TidBITS (1997-03-10)