1. With stiff brush, scrub clams with running cold water until free of sand. In 4-quart saucepan over high heat, heat 1 cup water to boiling. Add clams; heat to boiling. Reduce heat to low; cover and simmer just until clams open, about 5 minutes.
2. Remove clams; reserve clam broth. Cool clams until easy to handle. Discard shells; with sharp knife, coarsely chop clams and set aside.
3. Clam broth can be sandy at times. Let broth stand awhile until sand settles at the bottom of saucepan. Carefully pour clear broth into measuring cup; add water to make 2 cups if necessary.
4. In same saucepan over medium heat, cook salt pork or bacon until lightly browned. Add onion; cook about 5 minutes or until tender, stirring occasionally. Stir in flour, salt, pepper, and celery salt until blended; cook 1 minute. Gradually stir in clam broth until smooth; add potatoes; heat to boiling. Reduce heat to low; cover and simmer 15 minutes or until potatoes are tender. Stir in half-and-half and clams; heat through.
5. Stir in butter or margarine; sprinkle chowder with some paprika.