HH-I-536, FEDERAL SPECIFICATION: INSULATION SHEET, ELECTRICAL, NATURAL MUSCOVITE MICA (23 JAN 1952)

HH-I-536, FEDERAL SPECIFICATION: INSULATION SHEET, ELECTRICAL, NATURAL MUSCOVITE MICA (23 JAN 1952). Natural-muscovite-mica electrical insulation covered by this specification shall be Class-M, natural block mica. Unless otherwise specified the colors shall be either ruby or non-ruby, as specified.