So I accidentally set off my PFD today and bought a new CO2 canister to re-arm it.
In the picture below of the actuation mechanism in my life jacket I'm confused about the function of the black rotatable switch. It can be rotated about 270. Can anybody enlighten me as to the function of this black rotating dial or lock or whatever it is? I have looked online under the name of my life jacket which is a Marlin Explorer 150 and also under the name on the valve being UML micro but can find nothing. Any help would be greatly appreciated.

Is it the attachment point for the arming valve to
the jacket itself?
Mine is an auto switch and has what looks like a bolt head in the same position.

Yes thanks that looks like it performs a similar function (different model to mine tho) but I'm blowed if I can understand it and therefore what I should do with it. Mine is not an automatic inflating one.
If I understand it properly - don't do anything with it. It simply holds the value unit to the vest itself through the manifold. Or something.