Preheat oven to 325 degrees. Grease and flour 2 loaf pans. Cream together butter and sugar. Beat in eggs, add vanilla, then fold in mashed bananas. Fold in 2 c of flour. Measure two additional c of flour, reserving 2 T of this to coat blueberries, which are added as a last ingredient. Place remaining flour in a sifter, adding allspice, baking soda, baking powder and salt. Sift and fold into the batter. Sprinkle the 2 T of flour on blueberries, coat well, then fold into batter. Divide the batter between 2 prepared loaf pans. Bake for approximately 50 minutes. Test with toothpick to determine when done (should come out clean from the center).