From a look at the PCB it seems the 4kb declaration ROM is just part of it. The two MN234000 seem two 512KX8 masked ROMs, so my guess is that this card maps 1MB of Kanji font data into the address space, which seems to make sense.
These #188 development ROM Packs are indeed special: they are missing the required checksum and copyright and should not be accepted as valid ROM Packs by a standard TechStep. They contain beta versions of the existing ROM Packs and as such are historically interesting, but are not useful for...