First and foremost we should discuss the colour. A modern will look at this chasuble and think of this as liturgically blue, however as we have noted here before on various occasions (See: A Brief History of Liturgical Colours), looks can be deceiving. Certainly the medieval period saw a greater variety of coloured textiles used in vestment work, and one can even find some examples of blue being specified in some locations, but generally speaking blue textiles such as this were actually used as black or purple liturgically speaking. That might seem strange to us, spoiled as we are by the free-flowing availability of textiles, but earlier generations did not have this same luxury as we.
The velvet in question here is an example one of the most popular designs of the Renaissance. It follows the cammino-inferriata motif and type; a voided velvet that contains five-lobed corollas filled with pomegranates, thistles or other such designs.
Shape-wise this particular chasuble is a typical medieval cut. It is not fully conical but rather semi-conical -- meaning that a portion of the bottom of the 'cone' has been cut away, though not so much that its length at the sides would not still reach past the arms and hands of whomever wears it. In that regard, when worn, this chasuble would still have had the iconic folds we associate with conical chasubles, while also having the practical benefit of requiring less fabric and being lighter and less clumsy to wear.
Photos: Victoria and Albert Museum