A 19th century version.
Here’s a similar version from the December 24, 1879 edition of the Chariton (Iowa) Patriot:
Butter-Scotch Candy. — One pound of sugar, one-half pint of water. Boil as hard as possible without graining. When done add half a cup of butter, and lemon juice for flavor, if desired. Turn on a buttered dish, or, better, a marble slab, and, when partly cool, cut with a knife into small squares, and when cool a slight tap will break them off.
The vinegar acts to break apart some of the sucrose–we learned the value of that in the post for cream candy from this box.
For more on butterscotch, see the post for butterscotch crisps from Ceres, California.
From the box of A.D. from Lutz, Florida, by way of Pennsylvania in the 1940s, and originating in Ohio in the 1920s.
Butter Scotch Candy
1 cup sugar
1/4 cup molasses
1 Tbsp. vinegar
2 Tbsp. boiling water
1/2 cup butter
Boil ingredients without stirring to the hard crack stage.
Turn into a buttered pan.
When slightly cool break into squares.