Samsung SM-B310E archive, a 4.14 MB RAR tied to this dual-SIM feature phone. The name does not state the contents, which may be firmware, flash files or service documentation, so open it and check before use. For feature phone repair, such packages are typically used to reflash software with a box tool or to consult layouts when tracing display, keypad and charging faults. Make sure the model and hardware revision of the handset match, and back up the existing data before flashing.
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 @Schematic_mobile_iran. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.