Here is the 1N5398 diode specification sheet in PDF form, 42.7 KB, indexed as a schematic. The identical size to other 1N539x files suggests it is the shared family datasheet saved under this specific part name. Repair techs consult such sheets to confirm a rectifier's voltage rating, current capability and package before replacing it on a damaged supply board. It opens in any PDF reader. When substituting, pick a part with equal or higher reverse voltage and current, and keep lead spacing compatible with the PCB holes.
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.