@slaine That's an original ICO AdSpeed. You drop it into the 68000 socket then put your original CPU into the top of it.
Somehow it allows the CPU to flip from 7Mhz to 14. With the jumpers, I have mine always set to 14. But I can switch it to 7 via software any time I need to slow down (almost never unless you fire up Ultima, which has its timing set to the CPU speed, which is kind of hilarious).
This was the basis for Dunklee's inspiration for the 28Mhz accelerator he makes for the Parceiro