This decorative purse closure feeds a strap through the loop as an easy way to close a pouch. 
This purse mount is of a Hungarian style excavated in Sweden. They are dated to the 9th-12th centuries and were found at the Birka site in grave 93B. Although found in Sweden, This fitting is believed to be an exotic import as it is common on Tarsoly purses found in Hungarian and Kievan Rus sites. Two different examples of similar Tarsoly are held at the Egri museum.

Measurements:
L= 3 cm, W= 3 cm

You can read more about the Hungarian examples here:

You can see the original Birka artifact here: