These are made up Proto-Types, they are fully working drop in replacements for the rare 40010 in the Amstrad CPC 664 or 6128.

There are currently no known bugs, but it would help the project creator out greatly if any could be report via the above Github.
I will also sell these with the understanding that if there is a future update in the firmware you can send them back to me at your own expense (postage both ways) and I will update them free of charge.