Catalogued among schematics, this 213 KB PDF carries the part number 2N6426 and an RE suffix whose meaning the name does not give. A 2N number marks a JEDEC-registered discrete semiconductor, so the document should be its datasheet with ratings, characteristic data and pinout. It is used to identify terminals before desoldering, to check limits when a part has failed, and to select an equivalent. A second 2N6426 file exists in the collection, probably from another source, so compare both when details matter.
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.