For 356B T-6 and 356C models, this plate/grommet is installed under the dashboard; the fuel rod goes thru it. Molded in the face is: Z, A, R.

Tip: To shut off the fuel, turn the rod to "Z" (for Zu). To turn the fuel on, turn the rod to "A" (for Auf). And, turn to "R" (for for Res.) which means, "Get gas now; you only 1 1/2 gallons left in the tank!"