Lovely retro vest, well designed and well written.
Enjoyed making it.

things to keep in mind on this design:
motifs:
pieces are worked flat, so one must remember to reverse the order of the motifs when working the WS.

needle sizes:
it is easy to forget to change needles after starting with smaller needles for the garter st lower border.

more about needles:
one needs US 6 16” or 24” circular needles to work the arm opening garter stitch trim.
this can be avoided if one uses one’s US 6 in any longer length by knitting the trim in the flat, after the shoulder seam is done, but before the side seam is completed.
stitch up the few rows garter trim (under arm) along with the side seam.
(I already had both the shoulder and side seams completed, so I got a US 6 16” circular. I picked up the appropriate loops and then worked the arm opening garter trim flat so I could knit every row. I turned the work at under arm area, then, stitched that small seam closed when the garter rows were done.)

left and right fronts:
pattern does not write out the decreases for R front, only the L front.
to insure success, take a moment and write out those decreases, reversing the directions of the L front.

buttonholes:
one needn’t mark buttonholes (R front main piece).
buttonhole placement can be worked out mathematically.
for any given size, x stitches are picked up for the front band from the main piece and beginning lower garter stitch edge.
5 buttonholes.
2 stitches per buttonhole.
spacing can be worked out from there.

Modification:
worked 2 st rev st st between motifs to create a vertical line.
worked 2 rows rev st st between motif repeats for a horizontal line.

Seams:
sl st crochet, WS tog, RS up, US G/6 4.0 mm hook.

This design looks great with continuous motifs or blocked in with rev st st.

42” circumf, 18” ht before washing.
46” x 21 after MW cold, flat dry.
motifs relaxed upon washing.
If recipient wants it smaller, she can tumble dry it.