  We present a new calibration of the J-band absolute magnitude of the JAGB
method based on thermally pulsing AGB stars that are members of Milky Way open
clusters, having distances and reddenings, independently compiled and published
by Marigo et al (2022). 17 of these photometrically-selected J-Branch AGB stars
give M_J = -6.40 mag with a scatter of +/-0.40 mag, and a sigma on the mean of
+/-0.10 mag. Combining the Milky Way field carbon star calibration of Lee et
al. (2021) with this determination gives a weighted average of M_J(MW) = -6.19
+/- 0.04 mag (error on the mean). This value is statistically indistinguishable
from the value determined for this population of distance indicators in the LMC
and SMC, giving further evidence that JAGB stars are extremely reliable
distance indicators of high luminosity and universal applicability. Combining
the zero points for JAGB stars in these three systems, a value of M_J = -6.20
+/- 0.01 (stat) +/- 0.04 (sys) mag becomes our best current estimate of the
JAGB zero point and its associated errors. Finally, we note that no evidence is
found for any statistically significant dependence of this zero point on
metallicity.
