master cylinder gasket help

My 76 dart swinger is leaking brake fluid from the gasket in between the fluid "pots" and the big cylinder on my power brakes setup. I took off the front most piece and it seemed like the gasket was fine but it was plastic and metal with 3 gaps in the metal piece with a plastic piece that was over it which seemed undamaged. It was shaped to let the gap in the metal breath or leak. My question is, it that normal?? Or should the gaps be facing up so it breaths not leaks fluid.