Residual pressure valves are located in the master cylinder as required. Ie; 4 wheel drum master has a residual pressure valve each located in the port of the master right behind the brass line seat. A disc master has only one residual pressure valve located in rear segment port, you don’t want residual pressure on disc brakes.
the thing you circled is just and adapter to accommodate the brake line. You take the adapter out to get to the guts of the valve.
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