The MoonWatch Only book states (page 42) that the arrow shaped adjustment index on the balance bridge was black until model 105.002 in 1964... replaced by the metal index 1965 onwards.
Would it be possible that some 145.012-66 and -67 still came with the black version ? 馃槙
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I would say it is very likely that the black version was in use after that date. Omega didn't bin the old parts, just used them up over time. We see this in other cases, including applied logo dials and spear-tip chrono hands on transitional 145.022s.
Indeed subtle detail...
Along the service years the black index were replaces by the elongated lozenge metal one, although the inverse might be true if the watchmaker had a black version available. It's no perfect science 馃お