There has been a lot of speculation in the thread concerning the position (feathered or not) of the blades on the port engine and lack of blades on the starboard engine. Could it simply be that in the clockwise roll to the inverted position (having dragged the starboard wing as reported) the starboard prop made contact with hard the runway surface whereas the port prop only contacted the soft grass after inversion?
EC-ITP Metro III
http://http://www.airliners.net/photo/Fairchild-SA-227BC-Metro/1864958/L/&sid=573c5d7d2ba86bb9e1f1e6d26217894f