A 296 KB PDF datasheet for the 2N3390, listed as a schematic in the index and probably the same family sheet that also serves the 2N3391A, 2N3392 and 2N3393 entries of equal size. The name gives no manufacturer or revision. Technicians open it to confirm pinout, maximum ratings and gain before soldering in a replacement 2N-series transistor. Any PDF viewer handles it. Compare the case style and marking on the board part with the outline before relying on the lead assignment.
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.