error when trying to mount ext2fs harddisk, wrong magic nbr??

[Torben Brosten]

I'm trying to decipher the error message:

ext2fs: #ad/0x000a: wrong magic number 0x8b6 (expected 0xef53)

I've been reading

man magic
man file

but I have limited C experience. I see the references to ext2 in 
/usr/share/misc/magic, particularly:

 >>0x43a  leshort  ^0x0000001 (mounted or unclean)

Since 0x8b6 is much greater than 0x43a, am I to conclude that the drive was 
umounted incorrectly? If so, is there a way to use 'file' or some other utility 
to edit the offending magic number to 0xef53?