Sorry I am not too familiar with cars and stereos, so let me know if you need any more information.
As a result of my battery going flat, I discovered that my stereo has a security code... After sifting through all my paper work and searching every nook in the car, it was at this point that I realised that the previous owners had not supplied this code...
I've got a Blaupunkt 520 installed in my Holden Vectra '00. The (Model?) no. is 92 057 951 and also BP8389Y2711296 is printed above the barcode (some sort of serial I guess?).