I've attempted to take photos of the dice of some of these consoles underneath the glob tops, but unfortunately VRT never put the real part number on the die (the 555 palette one, for example, is marked "VRT VH3029-002"). The FC pocket one is just marked "K06", and is clearly a different totally different chip.
I have a suspicion the M320 chipset is the same as the 555 dancing cat one, just using a different feature set/config, but I haven't decapped it yet. The PCBs look similar, and they both use SQI flash whereas every other type of VRT chipset uses parallel flash.
So far I know at least the following unclassified chips exist, that may have some degree of Famicom compatibility:
- VT09
- VT16
- VT18
- VT32
- VT33
- VT368
- VT369