Lee,I am pretty sure that Zeiss will not offer tours. You have to be set up specifically to do this on a regular basis because occasional visits are so disruptive. Just think of all the precautions necessary:
Ensure no new product prototypes or components are on view.
Ensure no documents, drawings or brochures concerning new product development are on desks, pinned to notice boards, or visible on computer screens.
Check in reception to ensure no brochures illustrating a forthcoming new product have been delivered and are visible (I include this unlikely example as this actually happened at a company I visited).
Ensure that no chalkboards or whiteboards in offices or meeting rooms have anything on them that reveals new product plans or thinking.
And then there are the stats often posted around offices and factory floors that you wouldn't want to reveal to outsiders:
Production targets for this shift/day/ week/ month vs actual production achieved.
Ditto sales targets.
Scrapped product figures, customer complaints figures etc etc etc
Lee
What you say applies to any company or public establishment.
However many companies do manage to offer tours, and the risk of a brochure leak is in the end not much greater than that of someone forgetting a prototype in a pub
Customers and dealers like the climate of confidence in the process which a tour generates, and they are good PR. Among other things because they decisively clear up small but important questions like "where is the product really made" and also tech questions which interest specialists but which can be answered without giving away trade secrets.
And then also, there is the recruitement aspect ...
With a bunch of other PhDs, I took a tour of a satellite facility a few years ago in Germany, and in the lobby we were immediately asked whether one of us scientists would be interested in filling one of the available and very skilled jobs.
Edmund