Boardview archive named simply CAD, an 863 KB ZIP with no brand, model or board number in the title. The contents may be one or more .cad layout files or a viewer, so open it and identify the board from the file names inside. CAD layout files open in OpenBoardView, Boardviewer or FlexBV to locate parts, trace nets and find test points. Before relying on it, compare the board number and revision inside the file with those printed on your PCB.
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 @boardview_software_download. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Built-in OS tools7-Zip