Hello,
this is the normal layout of a QWERTZ keyboard on OSX.
<ALT-5> maps to "[", <ALT-6> to "]", <ALT-7> to "|", etc.
The standard adb-usb mapping works this way. And normally you want exactly this behaviour, e.g. with an QWERTZ AEK II keyboard.
So, to get "[" either on an AEK II (QWERTZ) with ADB-USB converter or on an QWERTZ USB keyboard, you press <ALT-5>.
But unfortunately, on the QWERTZ ADB NeXT keyboard, the printing on the keys mirrors in this area a PC keyboard:
Here <ALT-7> should map to "{" instead of "|", etc.
In OSX I've got the standard keyboard settings and behaviour.
Perhaps helpful: The key "7" gives in the matrix-scan function of matrix.c the value 0x1A when pressed, and 0x9A when released, "8" 0x1C and 0x9C, "9" 0x19 and 0x99. So the scan codes(?) on the NeXT ADB keyboard are basically sound.