Sorry OBAman you were just pipped at the post by Noyade as it is indeed the Sunrise S-1600 Areion.
However your understanding is correct whoever identifies the aircraft first posts the next challenge.
The Sunrise S-1600 was an American STOL short-haul transport aircraft first flown in 1968. The Sunrise S-1600 was produced in three models: the Sunrise S-1600P carried 24 passengers; the Sunrise S-1600C was a cargo transport version and the Sunrise S-1600S was a high-density commuter transport version with accommodation for 30 passengers. The Sunrise S-1600 was a high-wing cantilever monoplane powered by two AiResearch TPE-331 or Pratt and Whitney PT-6 turboprop engines providing a top speed of 531 kmh and a range of 1205 km fully laden.
Unfortunately I do not have a photograph of the aircraft.
Noyade has control.
Mel