Mounting unit for the holder of the gearbox (which was hanging below this ring). The rusty patch is where the heater unit was, in front of the firewall. The pipe coming out on the right is for the rain water that trickled through the ventilation flap in front of the windscreen, then through the heater unit, then in the recess which is barely visible near the left top edge of the photo (almost camouflaged by the rust).