A lot of head units in Japanese imported vehicles are locked by password which was set up by previous owner.
When you buy second hand car it makes sense to disconnect 12V battery and check if the unit is locked after power is restored.
In most cases car dealer would not have that password at hands.
Owner wanted to keep that high quality Alpine unit.
I have unlocked that Alpine EX009.
For doing that full dismantle was required and extraction of the password from the chip on board, using proprietary tools.
Applicable also to Alpine EX008, EX1000, EX09, EX8, EX9, X10, X11...
https://youtu.be/c1qVgZ2lQ90