HK has never seemed very interested in actually producing their own shotguns; however, realizing that many of their customers were also desirous of having a high-quality tactical 12gauge to go along with their other HK equipment--MP5's, UMP's, etc., they had seemed to try to forge a relationship with well-known Italian shotgun producers. They have, at various time, been partnered with Benelli and with Fabarm (there is no "s" in that name).
You'll find Benelli shotguns in this country both with and without the HK markings on them because weapons were brought into the U.S. during and after the partnership. You'll also find Fabarm shotguns both with and without the HK markings as well-for similar reasons. Benelli shotguns--especially the semiautos, are fantastic combat weapons. One of my former employers had 14" pistol-gripped M1 entry guns and they were magnificent. I also have nothing but good things to say about the HK/Fabarm semiautos, of which I personally own three. I've got two of the Tacticals and one older Gold Lion. The Gold Lion I picked up for next to nothing and it will be donated to the department, registered as an SBS and cut down to 14" for breaching/entry duty.
If you're going to purchase either an HK/Benelli or an HK/Fabarm, I don't think you'll go wrong at all, but keep this in mind: you'll have more selection with the Benelli (including spares) but you'll pay a good bit more than you will for the HK/Fabarm. Good luck!