With as many transmissions the Chinook has....chip lights were always a common event but rarely did we find anything but a bit of fuzz.
The two main gearboxes....driving the Rotorheads had Chip Detectors that could be pulled while in flight which was the way we identified which one it was as both were on a single segment light.
The joke done by the FE's was to take a Ball Bearing about three times the size of the Magnetic Plug and come forward to the cockpit asking what the Pilot's thought of the metal lodged on the magnet.
At one time engine gearboxes had a lot of serious chips being created and we were changing them with real frequency.
Some units had those nose boxes as we called them....actually come to bits with internal failures thus causing an "engine failure" situation through lost input to the rotor train.