The Routens seat cluster area has a nicer end to the seat stays , slender diamond shape.
There is a cable guide that angles the rear brake cable to line up with a hole in the seat tube.
The cable passes through the seat tube to a cable hanger infront of the seat stays.
Also the seat cluster is lugless.

To my eye the seat cluster area on the ops photos is less refined.
It has a cable guide and an outer cable that passes around the seat tube.
There then appears to be a braze on for the brake cable on the outside of the seat stays.

Here is a bike on Flickr that is described as a Jo Routens when it fact it is actually a Cycles de France bike.



Here is a Jo Routens with the nice seat cluster area.
There can be slightly different variations of this on Routens but you can see the quality difference between this and the ops seat cluster.



There are other makes that i can't name off the top of my head that have used this style roughly of ending the seat stays on the top tube.