This is a model of a Jon Renau traditional cap, which is a little nicer than you'll see in some of the lower-end brands with this cap construction. This is just to give you a general idea.
The biggest difference between this and the "open" cap construction is the top. Here, the top is covered completely with easily identifiable rose lace, which is entirely enclosed and makes the top of the wig heavier. In an "open" cap, this area would be wefted like the back and sides, making the top of an open wig lighter and cooler to wear.