This little jacket is particularly nice in a soft, drapy fabric: knits, light-weight boiled wools or faux suede, metallic knits, velour, eyelash fabric, faux fur . . . 
It can be reversible, and it can be easily lined. 
Embellish the jacket to your heart’s content! Trim the edges with a blanket or buttonhole stitch, or with binding, braid, a beaded fringe . . . 
1. Measure a rectangle 13 by 4".  Mark centre back at top edge, measure back neck E - F (3/8”) centered on the cb line. 
2. Fold C to E, and rotate A to G; then fold D to F, and B to H . 
3. Align the edges, and sew from G to H, hemming the neck edge to stabilize as you sew.

If the fabric will fray, finish all edges before sewing the shoulder seam.  To line the jacket, sew the lining fabric to the jacket fabric, right sides together, around all edges, 
leaving an opening for turning. Turn, press, and close opening, then proceed as above.
To sew by hand, use a whipstitch or backstitch with the fabric right side together, or, to use the shoulder seam as a design line, use a blanket, buttonhole or baseball stitch with fabric right sides together.
To sew by machine, try a narrow zigzag with fabric right sides together, or use an overedge stitch with right side out.

OPTION A Change the size to about 12 x 3 ½” to make a shorter jacket with 3/4 sleeves.
OPTION B Change the shape of the lower back edge.

OPTION C Add a swing to the centre back.
Make a paper pattern for half the jacket (6 1/2 x 4”), pivot from the top centre to add 3/4” at the cb lower edge. To keep the cb length at 4”, join to the original lower edge with a curve.