(3) In the case of an airship, the markings shall he displayed on the surface of the hull, or on the surfaces of the horizontal stabilizer and vertical stabilizer;
a) On the hull, they shall he located on the upper surface and on both sides around the point where the maximum Cross-section intersects its symmetrical axis at right angles;
b) On the surface of the horizontal stabilizer, they shall he located on the right half of the upper surface and on the left half of the under surtace with their top facing toward the leading edge thereof;
c) On the surtace of the vertical stabilizer, they shall he located on both sides of the lower vertical stabilizer.
Article 138. The height of the letters and numerals used for the nationality mark and the registration mark (hereinafter referred to as "each mark") shall he as follows:
(1) For an aeroplane and a glider:
a) In the case of displaying on the main wing surface: 50 centimeters or more;
b) In the case of displaying on the vertical tail ~g surface: 15 centimeters or more;
c) In the case of displaying on the fuselage surface: 15 centimetres or more;
(2) For a rotorcraft:
a) In the case of displaying on the bottom surface of the fuselage: 50 centimetres or more;
b) In the case of displaying on the fuselage surface: 15 centimetres or more;
(3) For an airship:
a) In the case of displaying on the hull surface: 50 centimetres or more;
b) In the case of displaying the horizontal stabiliser and vertical stabiliser: 15 centimetres or more.
Article 139. The width, thickness of lines, spacing, and colours of each mark shall be as follows:
(1) The width of each mark shall he two-thirds of the height, except for the Arabic numeral, one [1];
(2) The thickness of the lines shall he solid and one-sixth of the height of each mark;
(3) The spacing shall be more than one-fourth but not more than one-half of the width of each mark;
(4) The colour shall be one which may be clearly distinguished from the background colour of the place where each mark is displayed.
