This monogram is from a 14th century Manuscript Alphabet book which resides in The British Museum in London, England. 

Monogram:  U

Accents/Accessories: Textured background; Small loose bail; Central monogram

Size: 40.64 x 27.94 millimeters (1.60 x 1.10 inches)

Weight: 7.70 grams (0.27 ounces)

Sterling Silver Chain as shown: 16 inches - $25.00 or 18 inches - $35.00