The metal thing you see on the picture is nothing more and nothing less then a 512K memory expansion from C= (the original A501). A hard drive can be fitted internally but you should find it somewhere else! There are at least 2 IDE controllers which fit on the 68K socket, one being the ICD Ad-IDE the other (though very rare) would be a viper 520 or 530.
A harddrive needs power, if you open it up the power to the floppy drive should be split in 2 and lead to both the floppy and the harddrive.
Or maybe the floppy drive was removed all together and replaced with a hardrive? We need more pictures to be certain.
