Anyone Know What This Is?

I think the real purpose of that part is:

It is a intermediate gasket between the Master Cylinder and Brake Booster.....so that if the master cylinder piston starts leaking....brake fluid drips off the lip of that gasket and "Does Not" get into the rubber diaphram area of the Vacuum Booster.

I am good on rare parts.....I need door and trunk weatherstriping and a Windshield for the Duster though......or 73/74 "DART" Sport emblems