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tokens: lower-mass stars with which to anchor the comparison to the models. Still, it does appear that the model is significantly overpredicting the spin-down for the 0.6–0.8 M ⊙ stars, with the predicted median star in that mass range having a P rot = 21.0 days at 1.344 Gyr, ≈4.5 days more than what is observed. The four lower-mass NGC 752 members have rotation periods that are more consistent with what is predicted by the Matt et al. ( 2015 ) model, with the median 0.4–0.6 M ⊙ star predicted to have a P rot = 17.2 days. One possible interpretation is that we are seeing the evolutionary stalling observed in the comparison of Praesepe and NGC 6811 for 0.8–0.9 M ⊙ stars shifted to lower masses, with the 0.6–0.8 M ⊙ stars being the ones now rotating significantly faster than expected at this age. 6.2. Comparing Magnetic Activity in NGC 752 and in the Hyades and Praesepe Studies of observational tracers of coronal or chromospheric activity have uncovered a mass-dependent transition between active and inactive stars in open clusters (e.g., Kafka Honeycutt 2006 ; Douglas et al. 2014 ; Núñez Agüeros 2016 ; Núñez et al. 2017 ). The dividing line between these two populations shifts to lower masses in older clusters, indicating that lower-mass stars possess longer activity lifetimes. For FGK stars, these lifetimes are ≤650 Myr, as calibrated by observations of open clusters younger than NGC 752 (Hawley et al. 1999 ; Douglas et al. 2014 ; Núñez et al. 2017 ). Extending such measurements to older open clusters is a primary motivation of this work. Our knowledge of the chromospheric activity lifetimes of lower-mass stars currently relies on indirect calibrations, such as modeling the vertical gradient in H α emission line strengths as a consequence of dynamical heating in the Galactic disk (e.g., West et al. 2008 ). Our spectroscopic campaign confirms that the boundary between active and inactive stars has shifted well into the M dwarf regime in NGC 752. As noted above, there are three stars in our spectroscopic sample with formal detections of H α emission, but we do not consider these stars indicative of the location of the active/inactive boundary in this cluster. As Figure 11 demonstrates, even the modest activity signatures measured from these stars (EW >2 Å) make them clear outliers from the dominant cluster locus, and their moderate membership probabilities (50 P mem 80%) indicate that these stars may not be bona fide cluster members. Calculating the mean H α EW for NGC 752 members in bins of ( r − K ), as shown in Figure 15 , indicates that there is no transition to activity in NGC 752, at least within the domain of our spectroscopic survey, which includes stars with SpTs as late as ≈M2. Figure 15. Average H α EW as a function of logarithmically binned ( r − K ) for stars in NGC 752 compared to the younger Praesepe and Hyades clusters. The number of stars in each bin is along the top; the vertical bars show the σ for the bin, and the horizontal bars show