A 135 KB PDF for the part 27c512, placed in the schematic category but in practice a datasheet for a member of the widely used 27C CMOS EPROM family. No board, device or brand is named. The document lets a technician confirm pin numbering, supply and programming voltages, access time and erase conditions. That is useful when reading firmware from older equipment or burning a replacement chip in a programmer. Dump and keep the original contents before erasing, and match the speed suffix.
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.