A very small 12.3 KB PDF catalogued as a schematic and titled 27LV256-20I, a low-voltage 256 Kbit EPROM part number with what appears to be a 200 ns speed and industrial temperature suffix. Given its size it is probably a short summary or partial sheet rather than a full datasheet. It can still help with pinout and basic ratings when reading the chip in a programmer. Compare with the fuller 27LV256-20IL document, check the package on the board and save the original data 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.