Yes, from what I've learned, Olympos had some kind of co-op with Iwata in the 60's. Iwata had a background in toolmaking and sprayguns, while Olympos made airbrushes. When demand on airbrushes increased on the US market, Olympos couldn't cover production, so Iwata started to manufacture airbrushes of Olympos design. The Iwata HP-C and the Olympos HP-100C are very similar, especially when comparing older samples. The difference is mainly in finish and attention to details. Strictly from a feel and balance point of view, I would put older Olympos airbrushes as the best I've ever handled. Smooth, hand polished, and very spartan. Not that Iwata make bad airbrushes, but they are not as nice as Olympos better ones. The Microns are also an Olympos design, and even if spares fit between most of the Olympos HP and MP and their countaparts in the Iwata line, I rather use Olympos parts.
Olympos closed a couple of years ago, and what's left on the market is old stock. And my experience is that the last batches wasn't as good as the earlier.
Also, the Iwata Eclipse and Revolutions are not based on Olympos designs as far as I know, and Iwata has also made a lot of changes in the HP+ design. Fewer parts are interchangable today. I don't know if this has anything to do with manufakturing right or not, but the
Rumours tell that the owner of Olympos wasn't to happy to about how the furure of the brand looked, so he decided to throw in the towel after a career of 60-70 years of making airbrushes. He didn't trust his sons to continue the production and keep up the quality.