Trojan Light Phazer
Lightgun for the CPC Plus and GX4000.
Magnum vs Trojan
The Trojan looks exactly like the Magnum (in fact, both were manufactured by Trojan). The difference is that the Trojan connects to the CPC Plus 6pin AUX socket, while the Magnum connects to the Expansion Port. And, the Trojan maps the Trigger as Joystick button (rather than merging it with the Light Sensor signal).
The Trojan connects to the CPC+/GX4000's 6pin AUX socket:
Light Sensor ---> CRTC Light Pen Input Trigger Button ---> Joystick Fire 2 (Row9, Bit4)