A boardview (component placement) file (board 6050A2730001). Shared as “6050A2730001 MB A01(BVD) (4).brd” — a .brd file, 485 KB.
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 @ShareMan_Electronic_Files. 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.
OpenBoardViewFlexBVBoardViewerAllegro Free Physical Viewer (Allegro .brd only)