646 crossed the chasm with RE1156, the 16:02 St.Moritz - Chur, on 10 March 2012.
The perfect end to a near perfect day would have been to get a Ge6/6ii crossing Landwasser Viaduct in great light but 646 was an acceptable substitute and secured the "Ge4/4iii Of The Trip" award for repeatedly appearing when conditions were at their best.