That's my favorite Roleicord model, and it has my favorite lens on it too. They take beautiful portraits, and are sharp as the dickens in the center stopped down. Unless you need the solenoid, it looks a little goofy hung out to dry over there.
I'm pretty sure it's attached by using the pre existing screw holes that are under the front camera cover. They probably pulled the cover up on that side, took the screws out that are under there, put small holes in the cover, and screwed in the bigger chrome screws you see to attach that mount. They look like knurled screws, so you could quickly unscrew things to put the camera into a case again.