The selector switch has stencilled letters on it. As you face the fuel valve from the inside, the "M" for "Main" is on the right, and the "R" for "Reserve" is on the left. I'm told that the middle position is off, and I have seen a Ferret or two that had an "O" in the middle. I have never seen an indicator plate before, and there is no such thing listed in the parts manual. I have a lot of Ferret books, and the ones that show the fuel valve are all stenciled, like mine.

The fuel switch can be traced by following the tubing leaving the switch. To the left of the switch the tubing goes to the left side of the tank. To the right of the switch the tubing goes to the right side of the tank. The left is the reserve and to the right is the main. What I do after a fill up is to use the left side of the tank for about 30 minutes of fun and then switch to the right side which is the main. Doing this keeps the reserve clean and puts fresh gas in it. I had some old video recording tapes still in the box. They had a labeling page with them that had number and letters on it for marking the tapes. I took the R and stuck it on the left side of the switch and took an M and stuck it on the right side of the switch. Works Great. Later I found some 1/2 inch white with black letters at Walmarts (for mail boxes) and I bought an R and M and stuck them on the Ferret Hull behind the switch in the appropriate positions.