It was completing the icing trials, but is also the prototype for the 'long nose' model. Word at AAC was that the long nose would be going into production soon, with its own serial code (31xxx for Italian short nose 139, 41xxx for US short nose 139, 51xxx for long nose).
About the icing trials, there is a good article in either Vertical or Heli-ops (don't have it here) , showing the 139 behind the chinook-ice maker
