Android application package named Magnifier Camera, version 1.6.0, file size 2.83 MB. It presumably turns a phone camera into a magnifier, which some technicians use as a makeshift inspection aid for reading tiny component markings, checking solder joints or spotting corrosion when a microscope is not at hand. Install it on an Android device by sideloading the APK with unknown sources enabled. Only install packages you trust and scan them first, as APK files from outside an app store can carry unwanted code.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @esquemaseletricos. Enginerys does not host this file.