additional info to IC2 (SBW7) which may be helpful for identification....there is some sort of PWM signal measurable on PIN6 (IC6).
LED OFF 0V
LED disconnected 0-3V, various pulse lengths according to required LED intensity
LED intensity 1 0-3V, pulse length 0.06ms (shortest pulse)
LED intensity 2 0-3V, pulse length 0.5ms
LED intensity 3 0-3V, pulse length 0.8ms