  We observed HD 19467 B with JWST's NIRCam in six filters spanning 2.5-4.6
$\mu m$ with the Long Wavelength Bar coronagraph. The brown dwarf HD 19467 B
was initially identified through a long-period trend in the radial velocity of
G3V star HD 19467. HD 19467 B was subsequently detected via coronagraphic
imaging and spectroscopy, and characterized as a late-T type brown dwarf with
approximate temperature $\sim1000$K. We observed HD 19467 B as a part of the
NIRCam GTO science program, demonstrating the first use of the NIRCam Long
Wavelength Bar coronagraphic mask. The object was detected in all 6 filters
(contrast levels of $2\times10^{-4}$ to $2\times10^{-5}$) at a separation of
1.6 arcsec using Angular Differential Imaging (ADI) and Synthetic Reference
Differential Imaging (SynRDI). Due to a guidestar failure during acquisition of
a pre-selected reference star, no reference star data was available for
post-processing. However, RDI was successfully applied using synthetic Point
Spread Functions (PSFs) developed from contemporaneous maps of the telescope's
optical configuration. Additional radial velocity data (from Keck/HIRES) are
used to constrain the orbit of HD 19467 B. Photometric data from TESS are used
to constrain the properties of the host star, particularly its age. NIRCam
photometry, spectra and photometry from literature, and improved stellar
parameters are used in conjunction with recent spectral and evolutionary
substellar models to derive physical properties for HD 19467 B. Using an age of
9.4$\pm$0.9 Gyr inferred from spectroscopy, Gaia astrometry, and TESS
asteroseismology, we obtain a model-derived mass of 62$\pm 1M_{J}$, which is
consistent within 2-$\sigma$ with the dynamically derived mass of
81$^{+14}_{-12}M_{J}$.
