Boardview file in .brd format, about 211 KB, whose name gives only LI6, which looks like a project code but identifies no brand, board number or revision. Such files map every component position, pin and net on a PCB, so a technician can find where a rail goes, locate a test point or isolate the part causing a short. Load it in OpenBoardView, FlexBV or a similar viewer and match the outline, connector layout and markings against the actual board before trusting it, since the name alone cannot confirm the model.
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 @pepeelectronica. Enginerys does not host this file.
How to open a .brd file
The most common boardview extension. Several unrelated formats share it, which is why one viewer opens a .brd and another refuses it.