Every time I reboot our solaris 9 (SunOS 5.9 Generic_118558-19 sun4u sparc SUNW,Sun-Fire-480R) box,
I get the messages below:
# dmesg | grep dump
Mar 24 12:39:55 hostname savecore: [ID 346688 auth.error] initial dump header corrupt
Mar 24 12:39:55 hostname genunix: [ID 454863 kern.info] dump on /dev/dsk/c1t0d0s1 size 700 MB
Mar 24 12:48:08 hostname genunix: [ID 454863 kern.info] dump on /dev/md/dsk/d10 size 700 MB
Mar 24 12:48:22 hostname genunix: [ID 454863 kern.info] dump on /dev/dsk/c1t0d0s1 size 700 MB

Is this something I should be concerned about? Is this normal?

I checked our other solaris 9 machines and some have it and some don't.

core dumps for anything are not normal behavior. The only ways this could happen:

One process is signaling another with SIGABRT or some other sinal that forces a core dump. This is odd behavior and I've not seen it.

Some process itself had a bus error or a segfault, which means there is a problem with the process code. Or a shared library. This sometimes happens when there are upgrades or patches applied to a sytem.

It may also be that the process cannot do what it is supposed to do - maybe it has been started at the wrong time. Or run on a system that is not configured to do what the process expects. Or a control file for the process is corrupted....

Yes, you need to research it and fix it if possible.

Actually, this has nothing to do with core dumps per se, it is crash dump that is being dealt with here.