how many people work on an oil rig eg
Depends how big the rig is. A drilling rig would have between 40 and 60. Platforms are larger and are nailed to the sea bed. They vary between 80 and 160 though in busy times with a heavy maintenance program they can go to 200 plus.
A medium sized platform would generally have one changeover aircraft every weekday. The personnel are on 2 weeks on, 2weeks off so they changeover every fortnight.
19 out and 19 back X 5 days X 2 weeks equals 190 each way. Not always full so generally a bit less.
I don't think Cambodia was in the Rotordyne market. Third world countries used all sorts of aviation pictures for their air mail stamps. The same with banknotes. Before 1980 China used notes for every denomination and the 1 fen note, about 1.5 inches X 1 inch had a picture of a Russian copy of the Douglas DC3 on it.