19 CFR §12.61

1. (a)Fur-seal or sea-otter skins taken by Indians, Aleuts, or other aborigines under the authority of section 3 of the act, fur-seal skins taken under the authority of the Canadian Government, and fur-seal skins taken on the Pribilof Islands and other specified areas under the authority of section 4 of the act shall be admitted to entry if officially marked and certified as having been lawfully taken and if accompanied by a declaration of the shipper identifying the skins by marks and numbers as those covered by the official certificate.
2. (b)Fur-seal or sea-otter skins taken in waters or on land not specified in the act or in the fur-seal agreement with Canada or other fur-seal agreement shall be admitted to entry upon the production of evidence satisfactory to the port director that they have been so taken.