A 164 KB PDF catalogued as a schematic and titled 28C64B, the B revision of the 28C64 64 Kbit parallel EEPROM code. The name names no vendor or package. The datasheet should provide pinout, page write and data polling details, endurance figures and AC timing. It is useful when reading or rewriting configuration or firmware on older boards with a parallel programmer, and when checking a substitute device. Verify the full marking on the chip matches before trusting the timing values.
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.