zc.buildout's bootstrap.py changes all the time yet it doesn't have an embedded version number. It's also copied a lot into the source trees of other projects.

which-bootstrap.sh

#!/bin/sh
filename=${1:-bootstrap.py}
test -f "$filename" || {
    echo "there is no $filename here"
    exit 1
}
checksum=$(sha1sum "$filename")
case "$checksum" in
    0b63906b1c5d2eccbc9f727b0c1374c7c29f06a2*)
        echo "you've got the obsolete v1.x bootstrap.py"
        # was the current one for a loong time, until mid Oct 2013
        ;;
    2e4e6663df3de8b5ff1545a80acc3bca31d1fcaf*)
        # new v1 since mid Oct 2013
        echo "you've got the latest v1.x bootstrap.py"
        echo "http://downloads.buildout.org/1/bootstrap.py"
        ;;
    357f2fe2684c54339fb78ff447d8cbc127071633*)
        echo "you've got the obsolete v2.0 bootstrap.py"
        ;;
    ffbd56cd335be4bbab184eb8fc98f45fde41deec*)
        echo "you've got the latest v2.1 bootstrap.py"
        echo "http://downloads.buildout.org/2.1/bootstrap.py"
        ;;
    99a678df153dac9c5546f43cd55b5f27e0b07172*)
        echo "you've got the latest v2.2 bootstrap.py"
        echo "http://downloads.buildout.org/2/bootstrap.py"
        ;;
    *)
        echo "you've got some obsolete bootstrap.py probably"
        exit 1
        ;;
esac