Philip> This is on an 8600/200, booting from floppy with the image found at
Philip> ftp://ftp.netbsd.org/pub/NetBSD/arch/macppc/floppy/bootfloppy-980715.image.hqx

Seems like the image is far away old. 
Use 1.5 Release Stuff or 1.5K snapshot.

Release:
 ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-1.5/macppc/installation/boot.fs
1.5K snapshot:
 ftp://ftp.netbsd.org/pub/NetBSD/arch/macppc/snapshot/20001125/installation/floppy/boot.fs

Or is there any reason to stick that old version ?
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Makoto Fujiwara