The Selenus set you have is called the “Tulip Style”. This style was made in Germany from the 18th and 19th Centuries. They varied greatly in size and were almost always crafted from bone.
In 1616 Augustus, the Duke of Brunswick-Luneburg, published the first German chess book under the pseudonym Gustavas Selenus. Gustavas is an anagram of Augustus with one "u" replaced by a "v." The name Selenus comes from Selene, Greek goddess of the moon, a reference to Luneburg (Luna is Latin for the moon). In addition to chess instruction, his book contained excellent illustrations of contemporary chess pieces. German chess pieces at the time tended to be slender with nested floral crowns. The book was so successful that pieces of this pattern became known as the "Selenus” pieces. The pieces became taller, thinner, and more elaborate over time. Their apparent floral nature lead some to name them Garden or Tulip sets. Selenus pattern sets were commonly made in Germany and Central Europe until about 1914 when they were completely eclipsed by the more playable and stable Staunton Pattern, which was introduced in 1849.