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He did well to introduce the Kruskal-Szekeres coordinates in 1960 to the Kerr vacuum solution since the Kerr solution wasn't discovered until 1963. Kruskal M.D., Phys. Rev 119, 1743 (1960) and Kerr R.P. Phys Rev Lett 11, 237 (1963) Perhaps this is the tiny hint that he discovered more than just a coordinate system?