I've got a tri-wing screwdriver and disassembled the NDSL. At SL-1 Contacts, I could measure 3,3V. I used a potentiometer to put the voltage to every value between 0V (short) and 3,3V. But it didn't flash!
So there seems to be a newer NDSL, that cannot be flashed anymore!
So there seems to be a newer NDSL, that cannot be flashed anymore!