CREATE TABLE table_59711 ("Initial-syllable open/semi-open unstressed vowels" TEXT, "17th c." TEXT, "American" TEXT, "British" TEXT, "Australian" TEXT, "Examples" TEXT)

What is 17th c., when Initial-Syllable Open/Semi-Open Unstressed Vowels is 'o / /'?
SELECT "17th c." FROM table_59711 WHERE "Initial-syllable open/semi-open unstressed vowels" = 'o /ɵ/'
SELECT "17th c." FROM "table_59711" WHERE "Initial-syllable open/semi-open unstressed vowels" = 'o /ɵ/'