The James Webb Space Telescope (JWST) Near IR Imager and Slitless Spectrograph (NIRISS) has a seven hole non-redundant mask (NRM) in its pupil. The interferometric resolution obtained with the NRM provides a reliable measure of the magnification, position, and distribution of the PSF. The NRM image is Nyquist sampled at 4μm and operates with medium-band filters F380M, F430M, and F480M on NIRISS. We discuss cryovac CV1RR early NRM test data on the instrument. An image-plane, point-source model serves as a predictive tool for the NRM PSF, whose fine scale features' relative intensity can be used to measure detector non-linearities and determine its plate scale and rotation. We present a conservative estimate of NRM's wide-field astrometric performance. We present an analysis of the NIRISS plate scale and detector response as well as a prediction for NRM on-sky performance, taking into account measured intrapixel sensitivities, at fields, and detector linearity corrections.