We argue that the accuracy by which the isochron parameters of the decay
187Re→187Os are determined by dating iron meteorites may
not directly constrain the possible time-dependence of the decay rate and hence
of the fine-structure constant α. From this point of view, some of the
attempts to analyze the Oklo constraint and the results of the QSO absorption
lines are re-examined.Comment: 7 pages, 3 figures; v2, revised top sentence on p.