This monogram is from Gustave Boussenot, a French heraldic artist, from his book Chiffres & Monogrammes et suite de Composition Decoratives, Paris France, (1880). 

Monogram: BJ

Accents/Accessories: Round shape; Loose bail; Detailed border with oxidization; Raised monogram with shiny finish

Size: 53 x 42 millimeters (2.09 x 1.65 inches)

Weight: 19.50 grams (0.69 ounces)