Note 586 — VI INTERNATIONAL RATES
Reading edition
Those countries which were unable to adopt the metric system of weights were given liberty to substitute the ounce avoirdupois (28.3465 grammes), a half-ounce being reckoned the equivalent of 15 grammes, and 2 ounces the equivalent of 50 grammes.—Documents du Congrès postal international, Berne, 1874, p. 66.