This is a .tpx3c file that is the result of a fast mass microscopy imaging experiment of two overlaying grids. This file is a mass spectral image that can be converted into, for example, a set of .png images that correspond to mass peaks or into another mass spectrometry imaging (MSI) data file format such as .imzml. This GitHub page: https://github.com/M4i-Imaging-Mass-Spectrometry/fast-mass-microscopy-example contains example code and instructions to work with the file in this repository as well as some example outputs that can be generated from this file using the example code in the GitHub page. This .tpx3c file is intended to pair with the GitHub code to allow others to understand the method of fast mass microscopy image acquisition and construction.