Half-moon Yixing teapot.
This half-moon form teapot is rather special.
The form is inspired by the half-barrel shape of eaves tiles, typical of the Western Han dynasty, that had beautifully decorated end caps. some of which are semi-circular as in the shape of your teapot.
The calligraphy is a flowery form of ancient seal script and translates as the two characters:
Meaning "Handed Down" or "Tradition"
The artist's mark on the underside of the lid reads:
which interestingly pulls up not one mention in any of my references. This is not unusual as there were truly thousands of unrecorded potters and potter's marks -a single individual often had several marks throughout his active span of years.
The fact that Li Jinquan is unrecorded is that he's either extremely recent (unlikely looking at the piece) or ancient, in other words Qing Dynasty. I would go with the latter. This is also borne out by the lack of a kiln stamp on the base which is atypical and almost never seen on 20th century Yixing examples.
My opinion is that this is late Qing at the newest, and could be older.
I would give it an auction value in the range of $800 - $1250.
You should therefore insure it for at least $2500.
Very nice find!