Found another pic of the MC0005B while moving pics from the cpcwiki coppermine gallery. It's better resolution than the free.fr one, and has the extra resistor, too. Btw. good finding! I didn't notice that there was an extra resistor.
Hmmmm, only two 664 boards... is that all? Was the 664 discontinued when the 6128 came out? Or should there be also newer 664 boards existing?
Or, possibly 664s with newer 6128 boards inside (without PAL and with only 64K RAM installed), the 6128 board does have that option, but no idea if it that variant was ever produced?