When is a guernsey not a cow?

The 5th project for Nihon Vogue Year 2 is a sweater called a "Guernsey" (British) which is also known as a "Gansey" (Scottish). Having spent many of my childhood summers far from Alaska, in northern Wisconsin, the only guernsey I had ever heard of before is the kind that produces milk! These square shaped, hardy sweaters were developed centuries ago near the British Channel Islands of Jersey and Guernsey. A guernsey can be a dense knit, and is designed for hard wearing by hard working fishermen. The bottom edge is cast on in double yarn to provide added strength. The garment is knit in the round up to the underarms and then worked flat. Because they are worked in the round, the side seams are eliminated. A mock seam is provided by a single purl stitch on opposite sides of the garment above the welt. The guernsey sweater is distinctive because of the diamond shaped gussets under each arm which lends freedom of movement to the wearer. Each sleeve is worked in the round from the shoulders to the cuff and then finished with a double yarn cast off. This makes it easy for future replacement of worn out sleeves because they can be unknit (rip rip, rip) from the cuff and then re-knit back down anywhere from the upper arm through elbow to the cuff. I don't expect to be fishing quite enough to wear out the sleeves in my sweater! The front and back of the sweater is the same and historically, this fisherman's sweater was knit in 5 ply navy blue wool. Sometimes the initials or the entire first name of the wearer are worked into the garment above the welt. These letters can be a purl or seed stitch combination. A variety of neckband styles for guernsey such as ribbed, rolled, buttoned and folded can be used. There are several traditional stitch patterns for texture such as hearts, zig zags, trees, cables, seed and moss stitch as well as patterns designed by families. Many of the patterns have elements related to the sea such as stars, anchors, starfish, and diamond shapes.
In the last Nihon Vogue class, Jean explained the construction of the guernsey. We first drafted our sweaters in our 1/4 scale design notebooks and then did the full size pattern on metric drafting paper. Determining shoulder slope of either 3 or 4 cm was similar to how we had drawn up the raglan sweater, an earlier project. The guernsey sleeve extends from the shoulder point with elbow and wrist measurements added. A generous amount of ease is added to the sleeves and to the body. Gussets are added next. One half of the gusset will be worked in the round with increases and the upper half will be worked flat with decreases. I am still working out the stitch pattern design that I will use for the upper half of the sweater. My design uses a stockinette stitch for the bottom half, along with a garter welt and a channel island cast on which forms a sturdy but decorative picot edge. Seed stitch initials over 10 rows and possibly a mock turtleneck with buttons and a placket in the ribbing.
There are some excellent resources on knitting these sweaters that have such a strong heritage and compelling history:
Knitting Gansey's by Beth Brown-Reinsel
Cables, Diamonds, Herringbone by Sabine Domnick
Patterns for Guernseys, Jerseys and Arans by Gladys Thompson
Thus far, I am personally familiar with two sources for the 5 ply wool used for traditional guernsey's and highly recommend them both:
British Breeds 5 ply from Two Swans Yarns in Washington state
Yorkshire Mills 5 ply from Frangipani in UK