Runic Viking or Anglo-Saxon Ring, British Museum
The visible inscriptions seem to represent (l-r): th (thurisaz or thorn), a (ansuzn g t ? a ? (t/n bindrune) a p a
Approx 500-700 AD, didn't check details but must be Viking or Anglo-Saxon.
Futhark is the "runic alphabet" of the ancient Germanic tribes, comprising the Anglo-Saxons, Scandinavians and related Teutons.
Derived from the first 6 letters of the Runic Alphabet (much like the first two Greek letters that make up the same word) - Fehu (wealth), Uruz (aurochs...an extinct cattle), Thurisaz (Giant or Thorn - reflected in Scandinavian Thor, Anglo-Saxon Thunor), Ansuz (God-born - born of the Aesir), Raido (journey), and Kaunaz (illness / woe); the angular nature of the inscriptions is down to the ease at which they were cut into wood or hewn into stone.