Coating

<xs:element name="Coating">
  <xs:simpleType>
    <xs:restriction base="xs:string">
      <xs:enumeration value="aluminum"/>
      <xs:enumeration value="enhanced aluminum"/>
      <xs:enumeration value="enhanced silver"/>
      <xs:enumeration value="gold"/>
      <xs:enumeration value="mercury"/>
      <xs:enumeration value="silver"/>
    </xs:restriction>
  </xs:simpleType>
</xs:element>