penny-in-the pail
Not heard of it 411A. Care to elaborate please. (Flown turbines all my life)
Required; 2 quart white porcelin pail and a shiney US cent piece.
Place the penny at the bottom of the pail then fill the pail with jet fuel.
If you can read the date on the penny through the fuel...good to go.
Very effective, and was used by many JetStar, Sabreliner and Lear pilots years ago....and still sometimes noticed in use today.