[dev] cat unique deice identifier e.g. serial number

[hiro]

Anybody know a simple way to get a laptops device's serial number or
some other unique identifier which won''t identify all other same
models?

So far I came up with this:
(       for MA in `ls /sys/bus/pci/devices/*/modalias`
        do
                cat "$MA";
        done
) | sha1sum