Question answered to Gene via PM before I saw this post. The answer is....drumroll......:
If you look at a common scuba tank where the oring sits and the air comes out there is a hex head in the center. If you get the appropriate sized allen wrench, stick it in that hole (do NOT need to remove air from scuba tank first), rotate counter-clockwise, that center part will come out, it's just a big allen set screw....sort of. After that bit is removed the DIN adapter can screw into the scuba tank. Close the small valve on the side of the adapter, and SLOWLY open the scuba tank valve to fill your cylinder. AA S200's run around 2700 psi for best fill, they have a 122cc cylinder, so they fill really fast....just crack that scub a valve, it will fill faster than you are ready for the first time..close valve at 2700-2800psi. Open the small bleeder valve on the side of the adapter to bleed any air trapped between the tank and the gun cylinder, then unscrew the cylinder, reinstall on gun, and shoot!