Vintage/handmade ca1976 dress w overskirt to celebrate bicentennial, blue calico

Dress is previously owned, gently worn, minimal signs of wear. Very good condition, no stains or other damage. Dress is very well made. No tags or labels. Fabric is a medium weight cotton, no stretch. The overskirt has snaps to help keep in place. Dress is obviously custom made, waist laying flat is 12", pit to pit measurement is just shy 15" (no give in the bodice area). Looks like Butterick pattern 4261? No size tag