This directive should yield the value true when tested on any newer Power PC equipped Macintosh system and NaN when tested on an older 68K machine.
In MSIE version 5, it yields the value NaN regardless of the CPU, which is what you would expect on a non-Power PC system.
If you intend to hide this directive inside some comments, it must be done like this:
This does not appear to work in MSIE 5 for Macintosh.
Be careful with capitalization on this directive, none of the others seem to require capital letters but this one does.