Preheat oven to 300°F. Place ham directly on roasting pan, cut side down. Cover with foil. Bake 1½ to 2½ hours, or until internal temperature reaches 140°F. Meanwhile, combine jelly, ½ cup sugar, maple syrup, mustard, cinnamon, and nutmeg in medium saucepan. Bring to a boil. Reduce heat to low. Simmer, stirring often, until mixture is very thick and reduced by half, about 45 minutes. Remove from heat. Discard cinnamon pieces. Whisk in butter. Set aside. Combine remaining ¼ cup sugar and mustard powder in small bowl. Remove ham from oven. Increase oven temperature to 400°F. Remove foil from ham. Cool 5 minutes. Using pastry brush, brush ham with syrup mixture. Using a spoon, carefully press sugar mixture onto exterior of ham. Return ham to oven. Bake until brown and caramelized, about 20 minutes. Remove from oven. Place on cutting board. Loosely tent with foil. Let rest 10 minutes. Carve and serve. Serves 16–20.