For a 12 inch block, finished pieces sizes are...
Center square = 3 inches
Half square triangles in corners from 3 inch square
Quarter square triangles from 3 by 1½ inch rectangle
Peaky and spike unit is 4¼ inches square
Below are some other examples of the 1904 Star quilt block from other quilters...
Google Books - Alex Andersen
Google Books - Joen Wolfrom