Here's what I found so far:
According to "Jehovah's Witnesses in the Divine Purpose," 1959, pp.143,144,
in 1932, JWs didn't salute the flag of Germany, the USA, or Canada (it doesn't
say why other than due to allegiance to God, but I'm guessing it was due to
Rutherford's teaching of June 1 and 15, 1929, that the higher authorities of Ro-
mans 13 were God and Jesus, leading to ideas that human government was too
worldly, in an expanded idea of "worldly," and even controlled by Satan).
On June 3, 1935, Rutherford said he wouldn't salute a flag because doing so would
be to ascribe salvation to it (actually, it wouldn't be a matter of ascribing
Biblical salvation to it) and be unfaithful to God (it wouldn't). On Oct.6,
1935, during a radio broadcast, "Saluting a Flag," later published in the book-
let "Loyalty," he added that it would be worship of an image or representation
in disobediance to Ex.20:4-6 (it wouldn't--the Exodus section is meant as a ban
of worship of a thing rather than God, idolatry, not serving a country symbol-
ized by a thing).