@ Jope:
Found the info and you sir are CORRECT!
Got this at the Amiga Hardware Database:
- optional modules
monitor switch & scan doubler allows using one monitor for Amiga and CyberVision modes
doubles native Amiga 15 kHz modes to 31 kHz
connects to the video slot in one line with the CyberVision
a small ribbon cable attaches the cards
HD15 VGA connector
So eventhough it doesn't say it in the breakdown/info, the title clearly states that it is a monitor switch.

But I guess that means we could use the 64/3D internal header for an internal switch right?