Preheat oven to 325 degrees. Line a small baking pan with nonstick aluminum foil or coat with cooking spray.
In a small bowl, stir together the jam, mustard, pepper, and vinegar until blended. Reserve half (about 1/3 cup) to serve with the ham.
Score the ham with a knife by making several crisscross cuts in top of ham about 1/8-inch deep each. Place ham in a prepared pan and brush with some glaze. Bake for 1 hour, brushing with glaze every 15 minutes. Thinly slice ham and serve with reserved glaze.