You're right that it needs a code to function, but it's very unlikely that
the code will be written on the unit. Have you checked all the scraps of
paper and inside covers of the handbooks and service books? There's often a
space provided for the user to write the code in.

It's possible to get the radio out with a bit of brute force and ignorance,
unless you have the gadget that removes it properly, but I'm guessing you
don't! Your best option would be to speak to a Volvo dealer, who will be
able to retrieve the code for you. They might need the car, but may just ask
you for the registration or serial number of the radio. I suggest you speak
to them first to find out what info they want.  I'm guessing you're in the
UK, so the cost should be no more than about a tenner.

The good news is that once it's working, the radios and speakers are pretty
good - at least they are in the two '95 440s I've had.

Good luck,
Richard