The exposed contacts shall be self‐wiping, silver‐to‐silver and are of the reverse loop shoe type to increase contact pressure under fault conditions. All other current carrying contacts, including hinged end contacts, shall be silver ‐ to ‐ silver, unless sealed and insulated from contamination and corrosion. Internal sealed contacts may be either silver‐to‐silver or silver‐ to‐ copper. All exposed contacts, both fixed and movable, shall be replaceable in the field.