Herman Miller table  

Nickel's Worth o' Somethin'...
by the "Nelson Office"
Is the center height fixed?  Sometimes a similar appearance is seen on tabletops that slide and fold/unfold to double/halve in size.  I haven't seen such a thing from Herman Miller before, though.  Maybe a custom contract accommodation?
What's strange is that the top laminate surface stretches over the gap without apparent purpose or particular attractiveness... it's an odd way of resolving it, and seems like it could be an add-on (?).
 
Assuming you're looking to sell it, you could probably just call it a "scrapbooking table" and do well enough, I think-
 
 

Yes, the center height is fixed and is not adjustable in any way.  Both the table top  and the base have Herman Miller action office stickers, so I'm guessing if it was an add-on it came that way from the factory.  Must be a rare prototype 🙂

Vintage Action Office (both 1 and 2, yours is 1 by Robert Propst and George Nelson and Associates) was specified extensively for institutional use like public libraries and your table looks like a version that was used for reading, setting down books/magazines etc. or iif it came from an architect/engineer office to read blueprints and look at material samples.  It is not a rare prototype but something that Herman Miller did for specific clients/projects.  I have seen various Action Office configurations like library card catalogs with multiple drawers, a semi-private telephone table/booth, and others with hospital equipment on them.  The most desirable ones today are the configurations that are really useful and could easily cross over from the 1960's to the present time, from institutional to residential use and it is fits a standard doorway without taking the unit apart. 

Here is a better image of the labels.  The label on the darker background is on the steel cross brace and lacks "Action Office".  The other label is on the underside of the tabletop wood and says "Action Office".  Luckily it fits through a standard door without being taken apart.  However, it is not very functional, aside from drawing, since you can't set anything on it without it sliding off.