This is the next member of the 3rd Gruppe lead by Komtur ( sergeant) Karl. He is wearing MK III armor. The Mark III was never intended to replace the Mark II armour but instead was a specialised suit to provide heavier protection than the normal Mark II suit when fighting in conditions similar to that found on the Squat homeworlds, in mines, subterranean complexes or the tight corridors of a spacecraft. It has more frontal protection than the Mark II Armour, but the weight of the rear armour was lessened to compensate. The suit uses a heavy armoured helmet with sloping plates designed to deflect shots to the left and right, thus inspiring its name as the Iron Armour pattern. The helmet inspired the Mark IV and VI helmet designs. The wedge-shaped helmet (designed to deflect incoming fire from the front) formed the basis for the later distinctive Corvus Beak helmet of the Mark VI pattern. Iron Armour clanks and grinds with the slightest movement, making it all but useless in stealth operations. However, the presence of such an imposing and ancient suit of Power Armour is a great honour for all Space Marines and can greatly boost unit morale in combat. ( warhammer 40k wiki)