You need to contact the dealership. The circled number plus the vin will get you the code. It's free so don't pay for it. The circled number is 15 digits so take off the last one. It'll match the etched numbers on the side of the radio.
I've recently purchased a used RCD 510. Like so many before me, the previous owner did not provide the security code, as he probably assumed no code was needed. Could anyone advise as to if the sticker on the top of the HU is the security code? I'm referring to the last four numbers to be specific. If, not, the second picture provided below is of the serial number of the HU, correct?
Thanks in advance for any help that can be provided.