This isn't actually alpaca, but it's so close in appearance I've included it among the alpaca listings.

This sweater is made from a special high density wool from Himalayan sheep known commonly as Marco Polo Sheep, which originates from the explorer Marco Polo, who discovered them in his travels to the Orient, and described them in his 13th century book, The Travels of Marco Polo.

Characteristics:  The sheep is particularly known for its long, spiraling horns which have been measured having a span up to 140 cm (55 in). They have the longest horns of all sheep, with the longest individual horn ever recorded measuring 1.9 m (6.2 ft) and weighing 60 lb (27 kg).

This dense wool is very warm, and seen mostly in sweaters made and produced for people in the mountainous regions of the middle east. Because the wool is so dense, it doesn't have the ease of stretch westerners are accustomed to, so check the measurements below carefully, to ensure the fit won't be too tight.