PDF document of 121 KB covering the 2SK1455 semiconductor, listed in the schematic category. Apart from the part number, the name reveals nothing about the manufacturer, package or revision. JIS coding uses 2SK for N-channel FETs, so this is most plausibly a component data sheet. It lets a technician check pin order before taking diode-mode readings, and compare breakdown voltage, drain current and switching figures when sourcing a substitute. Check the marking on the physical part first.
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.