The pattern is really “New Classic V-Neck Sweater” from Men’s Knits, the version published in the US by Potter Craft.

I alternated two rows of each color for this, following the directions for the v-neck. I also slightly shaped the body for a v-shape, starting with 6 fewer stitches in the front and in the back, increasing 1 st each side every 15 rows until the correct number of stitches. For the back of the neck, I did 36 rows with each set of held-7 and used kitchener’s to join the ends. Not the prettiest, but it works.

The decreases don’t mirror. Instead, I’m doing this:
slant right:
 / ssk (slipping both knit-wise)
/  ss,p2tog tbl (slipping both knit-wise)
slant left:
\  k2tog
 \ p2tog