http://www.applematters.com/article/october-17-1998-system-85-released/
System 8.5 was Apple's first system that would run only on PowerPC hardware, instantly forcing obsolete status on all 68030- and 68040-based machines.
The wow factor of 8.5 centered around the inclusion of Sherlock, a search everywhere application that could find a file by name, by context or by searching one of six internet sites (users could add plug-ins to expand the number of sites). Under the hood improvements were manifold with System 8.5 and began to pave the way for OS X.
Mac OS 8.5 was released (CD only) for $99 on October 17, 1998.