Recipe: Coconut Custard Pie

Mary, I found this recipe in "New American Cook Book" published in 1950 maybe it is it.
Coconut Custard Pie
"Add 1/4 cup shredded coconut to custard mixture in recipe for custard Pie"
Custard Pie
Plain Pastry
3 eggs, slightly beaten
3/4 cup sugar
1/2 tsp salt
3 cups bottled milk ( ?...regular, I would guess)
1 tsp vanilla
Combine the eggs, sugar and salt. Add the milk and vanilla, and pour into pastry shell. Bake at 450 degrees in a preheated oven for 30-40 min. or until a silver knife inserted in the center comes out clean.
? silver knife? why silver?
Hope this helps