Nothing beyond the code 1SS309 appears in the name of this 69.5 KB PDF, so no device or board can be tied to it. The number follows the JIS designation for small-signal diodes, widely used by Toshiba, and the file is likely a datasheet even though it is indexed as a schematic. Technicians use such documents to identify a diode by marking, confirm polarity and package, and compare ratings with alternatives. Double check the footprint, since similar 1SS parts come in several SMD cases.
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 @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.