C-FFJM, a Perimeter Aviation LP Fairchild SA-227-AC aircraft was conducting flight PAG204 from Gods Narrows, MB (CYGO) to Winnipeg/James Armstrong Richardson Intl, (CYWG). While at approximately 2000 ft. asl, on a 4 nm final approach to Runway 31 at CTWG, the aircraft passed approximately 100 feet below an unknown airborne object. The object was octagonal in shape and bright red in colour. The flight crew did not make an evasive manoeuvre but reported the event to ATC. The aircraft landed without further incident.