Yep that strong Bauhaus-style reminded me on Delta, but in fact I'm a litte stuck here.
My (contradictory) source reports Delta was closed down in 1971 after all attempts to get into production were fruitless.
On the other hand there are pics featured which date from 1975...
So, I'm guessing it's a 1976/77 module van design based on old Delta 6/Durocar 1 concepts.