Originally posted by monochrome Asahi Optical Co and successors no longer exists. It was wholly merged into Hoya Corp. Pentax isn’t a company, per se. It is just a brand of cameras and lenses marketed by Ricoh Imaging Co. Ltd., and not even a trade name until 1957 or so. If Ricoh does anything to mark the 100th Anniversary of the Asahi Optical Co. It will be purely a marketing gimmick.
It's not quite fully correct... HOYA bought PENTAX in a hostile takeover and merged PENTAX into HOYA Group as multiple divisions. They eventually split off part of the original company as PENTAX Imaging (cameras, sport optics and related items) and sold it to Ricoh. The newly separate PENTAX company consisted mainly of original PENTAX corp staff and engineers. After Ricoh bought PENTAX Imaging, they renamed it to Pentax Ricoh Imaging Company and continued to use the old PENTAX headquarters in Tokiwadai. Ricoh later changed the name to Ricoh Imaging Co. Ltd., moved the operations (including original PENTAX staff) out of the old PENTAX building to their Ricoh office in Omori and transferred the Ricoh camera division into the PENTAX division.
It's still mainly the original (Asahi) PENTAX staff, including members of management and engineers (with the addition of Ricoh staff), but under a new name and owner. One can argue that PENTAX is more than just a brand, and that Ricoh Imaging, which is owned by Ricoh Group, is the successor company to (Asahi Optical) PENTAX Corp.
In my opinion, a 100th anniversary is more than just a marketing gimmick all things considered. And they are indeed planning to make a big deal about it. They will have some interesting products to mark the occasion according to what I've heard from my talks with them.