This one is Little Lines. The clever thing about Little Lines is the stitch pattern. It consists of little lines (hence the name) of knit stitches on a purl background, but since it's worked in the round that would ordinarily mean a lot of purling, something I don't enjoy. So you make it inside out! The vest is worked with purl lines on a knit background in the round to the armholes, flat front and back to the shoulders, and then joined at the shoulder seam with a 3-needle cast-off. Then you flip it inside out and voila! Purl background with a minimum of purling!
The vest is sized from 0-6 months up to 6-7 years, you can find it in my Ravelry pattern store here and my little boy had a fantastic time modelling it for me!