From the Pattern Description:

• … here is a seamless set-in sleeve worked from the top down, presented perhaps for the first time. It is a better-looking and better-fitting sleeve than the traditional one, having a very smooth cap free from irregularities. The method of working it relieves the knitter of any doubt concerning the position of the sleeve in the armhole, so that it cannot be spoiled by careless sewing or by miscalculations of the cap shaping.*

Location of Pattern: Basic Design No. 7 - page 81 - from Knitting from the Top.