wasn't Newfoundland a Dominion? When did it become one?
A very good question: Newfoundland enjoyed near-complete internal self-government from 1855 until the creation of an appointed Commission of Government in 1934. The declaration of the 1926 Imperial Conference stated that "The Governor of Newfoundland is in the same position as the Governor-General of a Dominion", indicating clearly that Newwdoundland was not then considered technically a Dominion, though enjoying many of the same rights in practice. Newfoundland was, however, defined as a Dominion by the Statute of Westminster (11 December 1931), so Dominion status lasted in theory for 26 months.
However, the Statute did not itself constitute a change in the territory's de facto constitutional status, and Newfoundland never wielded the same kind of diplomatic independence as Canada or Australia came to enjoy. I think the territory's real status is in some doubt, and have therefore not included it among the Dominions proper, i.e. those former British dependencies which possessed full effective sovereignty within the Empire. - David Parker