You can't re-program a masked rom but you can still read it. This adapts the pin positions of old 2364 masked roms to use the same pin positions as a 27C64 so that a regular EPROM programmer can easily read the contents of the masked ROM.

The 2364 and pin compatible masked roms were common in the 80s era of 8-bit home computers (Commodore VIC-20, Commodore 64, Tandy CoCos, etc). Before attempting to use this adapter make sure that the rom is pin compatible. If incompatible, at best you will create a corrupted ROM image, at worst you could damage the ROM. Most programmers will protect themselves from damage but do not assume this is the case.

Why do you need it?

While masked roms are generally robust they do fail, this adapter provides a simple way to read the rom image using an eprom programmer. In practical terms this is a way to verify a real rom against a known rom image. Or maybe to generate a new rom image where one doesn't exist.

Some modern recreations of old 8-bit computers have opted to use 27/28C64s instead of the original masked roms in the name of avoiding unobtainable parts. This adapter can also be used to fit original roms. If a larger capacity eprom is needed (eg. 27C256) this adapter will not really help.