Heckler & Koch’s “Operational Briefcase” is a clever system for covert carry of a submachine gun without the need to conceal such a large type of weapon under bulky clothing. By putting the gun into a briefcase, they gave security personnel a way to blend right into the business and executive type of environment. Of course, the idea has become rather well known, at least in some circles. It may not have quite the same element of surprise it once did, but it is still a remarkably discreet contraption.
Yes, the round thing by the normal trigger is a bar linking the handle trigger to the normal trigger.