ach, thats a bit of a pain... re-luming's not exactly difficult (though matching the colour of the "patina" lume isn't altogether straightforward), but it's a PITA with it being a Valjoux 7750 in there, because getting the flyback chrono hand back exactly in place afterwards, and on tight enough to cope with the stresses of the flyback motion without slipping - classic thing to see on older Valjoux 7750's is the Sweep Second Chrono hand being at 57,58s when at rest because it's gradually slipped backwards over the years.