"RDB was a converted ex TAA -100"
Nope. P2-RDB was ex VH-GKR, the first Talair Twin Otter. It was purchased in California (previous operator name alludes me) and ferried to PNG in 1971 by Brian McCook. It was also by far, the lightest Twin Otter around 2,980 kg empty. It was a -100, converted to -200 by installing the long nose.
Over the Kiunga Ok Tedi sector (where it spent a lot of it's life) it carried a better load than a Series 300. "Flash" held the record, twelve return flights in one day, carrying bags of drilling mud or cement.
The first ex TAA Series 200 aircraft came around 1973 through an agreement with Frank Ball then GM TAA. As part of the agreement we also got a Bristol freighter load of Twin Otter spares.