Boardview in .brd format for Apple logic board 820-3115, revision B. Apple uses the 820- prefix for its own board part numbers, and the name does not give the Mac model. BRD layouts open in OpenBoardView, FlexBV or Boardviewer, showing component placement, pin nets and test points so you can find a shorted part or measure a rail. Work with the 820-3115-B schematic alongside, and make sure the number and revision on the board match.
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 @cidschematicandboardviewofficial. 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.