root@fab-ux2:~
# for szDisk in $(ls /dev/sd?); do echo "$szDisk"; dd if="$szDisk" bs=1 count=4 skip=392; done
/dev/sda
GRUB4+0 records in
4+0 records out
4 bytes copied, 0,000154908 s, 25,8 kB/s
/dev/sdb
GRUB4+0 records in
4+0 records out
4 bytes copied, 6,0483e-05 s, 66,1 kB/s
/dev/sdc
dd: failed to open '/dev/sdc': No medium found