This is an adapter used for reading and writing the Kickstart ROM files to a replacement IC, used for replacing the MASK ROM in a number of 16-bit era machines including Amiga home computers, and SEGA Mega Drive and SNES game cartridges.
It adapts the pinout for the 42-pin 27C322/27C160/27C800 EPROMs or the 40-pin 27C400 EPROM to a 27C4096 4Mb JEDEC EPROM that the TL866 programmer is compatible with.
This is provided fully built and tested, ready to go. Just plug in your EPROM and plug the adapter into your TL866 to get started.
You can find the full documentation on GitHub.