I would have to get the whole story from Toshiya...I have heard it but I can't remember it exactly, so this is my vague recollection of it
Olympos made the micron Airbrush and sold the manufacturing rights to Iwata. Olympos has been making airbrushed for years and Mr Olympos did not really push his products where as Iwata did therefore Iwata became more popular.
Mr olympos wanted to retire and he tried to get one of his Sons to continue the business, his Son did not want to do so and went on to make Richpen I think. Mr Olympos sold his complete ivnevtory to Toshiya Takeshima years ago and Toshiya is not selling online. The inventory contains more than a 100,000 airbrushes.
Olympos and Iwata are the only airbrushes manufactured in Japan and I have a feeling that Iwata was made in the Olympos factory for some time. So I am sure there are interchangeable part just like headlights for cars
If you ask us at Olympos about exchangeable parts between Olympos and Iwata you will not get an answer as it is in our best interest to sell parts for Olympos airbrushes only. Sorry we are not here to support Iwata spare parts, but we will not stop you from purchasing an Olympos spare part....just don't ask us if it fits an Iwata
As mentioned in the beginning that I think that this is how the story goes....if you wish for me to expand on it or clarify it I will then speak to Toshiya and get the answers.