Origin unknown: Recipe for chewy blonde brownies

I'm having dinner with friends tonight and naturally, since I haven't been eating a lot of sweets lately, I offered to bring dessert. Not wanting to do anything too ambitious, I got to thumbing through my ancient index-card file of recipes and found this one for blonde brownies. The card is stained a little; I copied the recipe by hand probably more than 20 years ago, and I have no idea when or where I got it. These dessert bars are delicious, and very easy to make. Sorry I can't acknowledge my source.

Blonde brownies

2 cups flour
1 tsp. baking powder
1/4 tsp. baking soda
2/3 cup butter
2 cups firmly packed brown sugar
2 eggs, slightly beaten
2 teaspoons vanilla
1 cup semi-sweet chocolate chips
1/3 cup chopped nuts
1/2 cup grated coconut

Mix flour, baking power and soda in a small bowl. Melt butter. In a mixing bowl, combine melted butter and sugar. Blend in eggs and vanilla. Add flour mixture gradually, mixing well after each addition. Grease and flour a 9-by-13-inch baking pan. Spread batter evenly in pan. Sprinkle with chips, nuts and coconut. Bake 30 to 40 minutes at 350 degrees, until a knife inserted comes out clean. Cool in pan. Cut into 48 bars.