Boardview file in .brd format for a board labelled n91-d, about 292 KB. The name gives no brand or revision, so confirm that the board code matches the PCB before relying on it. Boardview files show component placement, part numbers and net connections on both sides of the board, letting a technician locate test points, find where a rail runs and measure resistance to ground when chasing a short. The .brd format is commonly opened with OpenBoardView, FlexBV or BoardViewer.
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 @one5technology. 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.