Here is another picture of the prototype phoenix.
The shroud is off a standard production phoenix.
Unique features include:
Crude stamping rather than the elegant standard phoenix engraving.
Edges are all softer (not as sharp) as on a standard phoenix.
Breech actuating cover on right side of body is raw.
Early style feedblock with two small arms protruding out of either side to attach the breech plate.
Can’t remember the differences internally (or possibly never took it apart to check?).