Looking for information or spec sheet on an old PROM/EPROM chip
My end goal/hope is to get the details on these chips so that I can properly get the data dumped


You do not need details for the EEPROM, you need programmer which would have this chip in the list of supported devices. This programmer will read data from these chips for you.

But if you are going to design your own circuit to read these chips (which I guess will be harder than locating programmer device), you can refer here or any other datasheet site. HN is Hitachi version of standard 27256 UV-erasable PROMs.