Becker built factory radios for several makes, and the code comes from the serial on the unit’s casing label. A Becker radio never shows its serial on the screen, so the unit has to come out of the dash.
Mercedes-Benz (Audio 10, Audio 30, Special, Exquisit, Grand Prix): the label carries the model, like BE 6023, and an eight-character serial. Some Becker radios take a four-digit code, others a five-digit one typed on the preset buttons, so the form asks what your display wants. Mercedes radio code.
Chrysler, Dodge, Jeep: a 14-character serial starting T00BE. Chrysler · Dodge · Jeep.
Renault: the eight-character serial off a Becker unit, when there is no precode on the label. Renault radio code.
Check before you enter it. A Becker code is for a Becker unit: make sure the radio itself says BECKER on the front panel or on its label. If it does not, the code is not for your radio.
On the label on the casing, next to the BE model number. The radio never shows it on the screen, so the unit has to come out of the dash.
The same Becker serial gives a different code on four-digit and five-digit units, so the display decides which one is yours.