For the third time in two months, a booby-trapped sign against Jews in Russia has caused injury to well-meaning passersby - but this time it was fatal. A Russian navy officer was killed yesterday when he tried to remove a sign in a town not far from Kaliningrad. The sign, dug into the grass near his home, stated derogatorily that a man living in the area was a Jew. The officer tried to remove the sign, somehow triggering a hidden explosive to detonate. He was killed, and another woman passing by was seriously injured. In an earlier incident, a woman was temporarily blinded when she attempted to uproot a similar sign; public and private Israeli sources helped fly her to Israel and receive treatment that restored her sight. Two Russians were injured in a similar incident several days ago.