KWA LM4 PMAGS - Teardown Guide

[MultipleParadox]

Hi all,

Anyone have some kind of guide to open up these mags?
I cannot, for the life of me, find a way to get to that release valve.
Couldn't find any guide, tutorial, exploded diagrams on the interwebs anywhere

I removed the top screws, a pin, could remove the rubber lip and partially see the valve in there, but that's as far as I can get.

Any infos are welcome

Thank you