Mercedes radios unlocked online — Becker Audio 10, Audio 30, Special, Exquisit and Grand Prix units answered from the serial on the casing.
A Mercedes head unit that has lost power asks for its code and never shows the serial, so the unit has to come out of the dash. Becker units release with a pair of U-shaped keys pushed into the holes at the corners of the fascia.
On the label you will find the model (BE 6023, BE 2010 and similar) and the serial. Send both — the model tells us which family the unit belongs to.
Some Mercedes units carry a longer serial instead, beginning DB — for example DB0920R1000019. That one we look up whole, and it needs no preset count: send it exactly as printed and nothing else.
Why we ask about the buttons. Becker codes are typed on the preset buttons, and the code table depends on how many of them the radio has: a four-button unit can only produce digits 1–4, a six-button one digits 1–6. The same serial therefore has a different code on a four-button and a six-button radio.
That is why the form asks. With the button count there is exactly one right answer and you get it on the spot; without it, a guess could hand you a code your radio cannot even accept. The manufacturer tools ask the same question.
The serial is on the label on the casing, next to the BE model number:
R2035446
A locked unit shows CODE and waits for the preset buttons.