I was a pilot for Pan Am and spent a lot of time in Hong Kong and Japan during the 70's and 80's. I saw some of the first Chinese pearls in Hong Kong then and didn't particularly care for them.
They were making an imitation pearl then that looked pretty good. I forgot the process they used, but I bought a bunch of them to give to my daughters and relatives.
In Tokyo I bought my wife a beautiful akoya necklace and it looks as good today as it did then because the nacre was much thicker then. During that period they would grow from 2 to 3 years.
The yen was much much lower than it is now, so its too bad I didn't have forward vision so I could have stocked up on akoyas, especially the Mikimotos, and I would now have a valuable collection.
Bill