It is packaged in a small, worn, red box displaying a picture of steak with the words 'Salisbury Steak' at the top and 'now with Gravy!' at the bottom. When consumed it restores some Hit Points and Starvation, but also gives a small amount of radiation.
↑Fallout 2d20 Rulebook p.157: "A ready-to-eat meal of ground beef mixed with bread crumbs, onion, and egg, served with gravy. The meal is pre-packaged, preserved, and sealed for freshness, and requires only heat to be made properly edible again."