This is the premium beef sandwich, where the meat is the luxury and the bread is the frame. Heavily marbled wagyu seared rare, thin roast beef, grilled beef tongue, the named regional brands: the sandwich is a way to show a prized cut, often at a high-end counter and a high price. The defining fact is that the beef is chosen first and everything else is built to flatter it.
The craft is the cook and the restraint. Wagyu is seared hard and kept rare so the fat softens without rendering away, then sliced thick enough to read as steak; roast beef is cut thin and laid in loose folds. The sauce is measured, a sharp or savoury note that lifts the fat rather than masking it, and the bread is soft and neutral so it carries the meat without competing. Over-saucing or over-cooking wastes the cut, which is the whole risk.
The variations are the cut and the region: seared wagyu and wagyu steak, roast beef in its plain and wagyu grades, Sendai beef tongue, the Kobe, Matsusaka, Omi and other branded beefs. Each is one premium cut given a bread, and each deserves its own article rather than being crowded in here.