Baked Ham with Molasses Crumb Topping

1 boneless cooked ham (3 pounds)
2 tablespoons butter or margarine
1 tablespoon firmly packed light brown sugar
1 tablespoon molasses
1 teaspoon prepared mustard
1/4 cup dry bread crumbs

Preheat the oven to 325 degrees. Score the top of the ham into diamonds. Place the ham on a rack in a shallow baking pan. Insert a roasting thermometer in the center. Bake for 1-1/4 hours. Meanwhile, In a small saucepan, melt the butter over moderate heat. Stir in the brown sugar, molasses, and mustard. Stir in the breadcrumbs. With a large spoon, spread the crumb mixture over top of ham. Bake for 15 to 30 minutes more or until thermometer registers 135 degrees. Cover with foil and let stand for 15 minutes before carving.