Mendi. I'll meet you half way - it was before Talair took over Macair around 1976 to 1978, so my guess would be around 1972 - and that is over 35 years ago.
Jim. I'm going to come up with a long shot guess here - I think you may be referring to a wing off Junkers Ju53/3M VH-BUU, which was pranged at Baiyer River around 1958, on the day Bobby Gibbes sold out to Ansett MAL. Ansett decided not to recover the aircraft, the fuselage, minus the wings, rotted away for years. I suspect you may have found a wing somewhere in the Highlands. I can't think of any other similar size aircraft prang in the Highlands that the wing may have come from? (Unless parts of Peter Arnold's Skyvan were recovered from Mt Gilluwe.)
The big difference was of course, that the Ju52 had corrugated skin, versus the DC3 smooth skin.
That is my best guess......
I'm sure the short lived Cessna 421B was the first Government aircraft with the P2-PNG registration. Don't recall the Moresby Gliding Club's King Air registration but think P2-PNG next went on Big Julie's Grumman Gulfstream II?