the blue limit lines in Figure 4 are identified.

A similar procedure is applied to M 67, except that a 30$^{'}$ (apparent diameter of 25$^{'}$; Dias et al. 2002) radius and fiducial $\pm$ 0.10 mag in $(g-r)_{0}$ is used. Based on this selection method, there are 195 (234) and 61 (64) for NGC 2420 and M 67, respectively. The first listed numbers indicate the stars with available estimates of \[Fe/H\] from the SSPP, while the quantities in parentheses represent the number of stars with available radial velocities (RVs) . Additional cuts, based on the derived metallicity estimates and RVs, are described below.

Determination of Overall Metallicities and Radial Velocities of the Clusters
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In order to investigate the accuracy of our derived metallicities and RVs, we now consider the global distribution of these parameters obtained from the current version of the SSPP for the likely cluster members. In this section, we describe a method to best isolate “true member stars” from the spectroscopic samples described above. We then use these subsamples to determine our best estimates of the overall metallicities and RVs of the clusters considered in this study.

Selection of True Members
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We establish the criteria for carrying 