Pigeon Spout is a nickname given to these teapots by early Taiwanese collectors. This shape was specifically designed for Japanese market and pitcher remains pigeon.
Because Japanese tea leaves are generally much smaller than Chinese leaves and can get stuck in single hole teapot 18 hole fine filter was developed. Plus the the shape of pitcher is fatter like a pigeons chest. 
 
Although these pots were perhaps made for Japanese tea, their clay is wonderful to enhance dark teas such as old Sheng, Shou Pu-Erh or LiuBao.
 
Period: 1970s
Weight: 145g
Volume: 164ml 
Filter: 18 holes
Bottom Seal: China Yixing 7:3