The cast on edge starts at the top of a sleeve, goes down the edge of the sleeve on the front, then up the other edge of the sleeve on the back, across the back of the neck, down the back of the other sleeve and up its front.
Two decreases are worked each row resulting in the diagonal line along the back sleeve. When the sleeves are complete the decreases stop. Instead two increases are worked each row which become the diagonal lines on the front. The cast off edge goes down the side past the button holes, along the bottom right around the jacket and then up the other side past the buttons.
There are two seams, along the top of each sleeve.
I haven't found the right buttons yet - the ones in the picture are just laid on the jacket to show where the buttons are.
Pattern from the Sunday Times Magazine, by Elizabeth Zimmerman, late 1970's. Double knitting yarn in garter stitch, took about 8 days to make.
There are a couple of free patterns available that are variations on this theme: