This is a fascinating and rare piece of framed artwork. We have done some research to try and find out more, see below.
It measures approximately 15cm in diameter. 
It appears to be either eggshell or translucent porcelain. 
Eggshell porcelain was introduced in the Ming dynasty during the reign of the emperor Yongle (1402–24). It reappeared in the reign of the emperor Chenghua (1464–87), and later Yongle wares were copied under the emperor Wanli (1572–1620). The paper-thin porcelain again occurred during the Qing dynasty (1644–1911/12), especially in the reign of the emperor Kangxi (1661–1722), in famille verte and famille rose porcelain, chiefly in bowls, plates, cups, and saucers. The manufacture of this porcelain is complex and time-consuming.
https://www.britannica.com/art/eggshell-porcelain
Translucent porcelain, also known as translucent china or porcelain china, has been a cherished art form for centuries. Its origins can be traced back to ancient China, where artisans honed the craft of creating delicate porcelain that could transmit light. Today, the art has evolved into a sophisticated fusion of traditional craftsmanship and contemporary design, resulting in breathtaking works of art and functional objects that are as captivating as they are useful.
Throughout history, translucent porcelain has played a significant role in various cultures around the world. In China, it is deeply rooted in their artistic heritage, symbolizing purity and perfection. In Europe, porcelain was once considered "white gold" and was highly prized by royalty and nobility. Today, translucent porcelain continues to be a symbol of refinement and elegance, connecting us to centuries of craftsmanship and artistry.
https://thebrightangle.com/blogs/the-bright-angle-blog/the-art-of-translucent-porcelain#:~:text=Translucent%20porcelain%2C%20also%20known%20as,cherished%20art%20form%20for%20centuries.
This piece depicts what appears to be Chinese junk boats, which would make sense if it is eggshell or translucent porcelain.
A junk is an ancient Chinese sailing vessel design still in use today. Junks were developed during the Han Dynasty (206 BC–220 AD) and were used as sea-going vessels as early as the 2nd century AD. They evolved in the later dynasties, and were used throughout Asia for extensive ocean voyages. They were found, and in lesser numbers are still found, throughout South-East Asia and India, but primarily in China, perhaps most famously in Hong Kong.
https://www.album-online.com/detail/en/MTUyNDViMA/junk-ancient-chinese-sailing-vessel-design-junks-developed-dynasty-bc-alb5529718
The artwork is definitely handpainted. Observed through a magnifying glass it is possible to identify the brush strokes. Research suggests the use of overglaze china paints. These are made of ground mineral compounds mixed with flux.The flux is a finely-ground glass, similar to porcelain glaze. The powdered paint is mixed with a medium, typically some type of oil, before being brushed onto the glazed object.
On further research the baroque brass frame is most likely from a different period. The intricate metal frame with floral details and feet suggests it could date to the late 19th or early 20th century, making it likely Victorian or Edwardian in style circa 1880-1920.  The craftsmanship hints at a decorative, functional object, possibly a vanity or display piece. 
The maritime theme of the porcelain disc would appeal to this era as it was popular in decorative arts of the Victorian and Edwardian periods. Their function was to highlight the skill of the artist while adding elegance to a room.
We suggest if you buy this to research it further! It is a lovely piece, potentially with significant decorative and historical value.
The porcelain disc is in amazing condition. The brass frame is showing some signs of wear, arguably commensurate with age.