This is a small Japanese case iron teapot 12 fl oz with NO LID as shown.

(here is all the research I've compiled):

Nailhead, Green Cast Iron Teapot 12 oz Japanese cast iron teapot tea pot

** lid needed is a 1-7/8 ID dimension 2-3/8" OD

color:  kambin green

Design:  Nailhead 

Origin:  handcrafted in Japan

Brand:  Unknown

design:  nailhead pattern

size:  small, 12 fl oz

Capacity:  12 fl oz or 1-1/2 cups (.35l)

Dimensions:  

Weight:  1 lb. 11oz. (w/filter no lid)

Material:  cast iron or tetsubin

stainless steel strainer tea filter (used)

infuser basket or  stainless steel  screen strainer tea filter included

trivet (coaster) not included



History:  This classic teapot is made from sturdy iron and has enamel coating on the interior to prevent rusting. It also comes with a removable stainless steel tea filter. This teapot is cast in a stylish flat saucer shape and design with bamboo patterns. Cast ironware heats evenly and retains heat well and is praised worldwide for their beauty, strength, and superb quality. Please note that this teapot should not be used directly on stovetop to heat water.

Historically during the mid 19th century as infused tea drinking became more popular in Japan, tetsubin or cast iron teapot evolved from being a kitchen item to being a status symbol used to serve tea. Many nobles cherish their teapots as treasures and are kept in the family for generations.

Let me know if you have any other questions.

Thanks for looking.