Vintage Master Recipe for a variety of Muffins

I love recipes like this. Ones that give  you a basic recipe and then you add or subtract a few ingredients to change it up.
This is a Master Recipe for muffins from the 1923 Royal Baking Powder Co.'s  Making Biscuits cookbook.
I found this recipe and the picture of the original book at Recipecurio.com.
If you click on the picture of the cookbook it ought to enlarge enough to read the ingredients although I have posted the recipe below the book.

THE ROYAL MASTER RECIPE FOR MUFFINS
2 cups flour
3 teaspoons Royal Baking Powder
1 tablespoon sugar
1/2 teaspoon salt
2 eggs
1 cup milk
4 tablespoons melted shortening
Sift together flour, baking powder, sugar and salt; add eggs, milk, melted and cooled shortening to make a stiff batter; mix all together well. Half fill greased muffin tins and bake in hot oven (400°) 18 to 20 minutes. Makes 14 muffins.

TEN DELICIOUS VARIATIONS OF THE MASTER RECIPE

BLUEBERRY MUFFINS
Add 3 tablespoons sugar to 1 cup washed and well drained blueberries; sprinkle with flour and add to batter in Master recipe. Half fill small greased muffin rings or tins and bake in moderate oven (375°) for 30 minutes. Canned blueberries carefully drained can also be used. Makes 24 small muffins.

CORN MEAL MUFFINS
Follow Master recipe using 3/4 cup corn meal and 1 1/4 cups flour; add 1 tablespoon more sugar (or omit all sugar) and use 1 egg instead of 2. Makes 12 muffins.

CRUMB MUFFINS
Take 2 cups stale bread crumbs and 1 cup flour instead of 2; add crumbs to other dry ingredients and follow Master recipe. Makes 12 muffins.

GINGER MUFFINS
Sift 1/4 teaspoon soda, 1/2 teaspoon ginger with dry ingredients in Master recipe; use 1/2 cup molasses and 1/2 cup milk instead of 2 cups milk; 1 egg instead of 2 and 2 more tablespoons shortening, and bake in slower oven (375°). Serve hot with butter. Makes 16 muffins.

DATE OR FRUIT MUFFINS
Follow Master recipe using 1 egg instead of 2 and little less milk. Flour 2/3 cup chopped and pitted dates or seedless raisins and add to batter.
For a sweet fruit muffin add 1/4 cup more sugar.
For a delightful variety use 1/2 cup finely chopped candied cherries and citron instead of above fruit.
Makes 12 muffins.

POPPY MUFFINS
To the muffin batter of master recipe add 2 teaspoons poppy seeds and bake as directed. Makes 12 muffins.

GRAHAM GEMS
Follow directions for Master recipe but use half graham and half white flour, 1 egg, 4 teaspoons Royal Baking Powder and 2 tablespoons sugar. Makes 12 gems.

RASPBERRY DAINTIES
To muffin batter in Master recipe stir in 4 tablespoons raspberry jam. Strawberry or other jam can be used in same way. Makes 14 muffins.

CHOCOLATE MUFFINS
Add 2 more tablespoons sugar to Master recipe and stir 1 1/2 squares (1 1/2 oz.) grated chocolate in batter just before putting in tins. Makes 14 muffins.

COCOANUT MUFFINS
Follow Master recipe using 1 egg instead of 2; omit shortening and add 1/2 cup shredded cocoanut. Bake in small greased muffin tins. Makes 24 small muffins.