Vtg Victorian Ornate Cameo Portrait of The Boy Blue by Thomas Gainsborough

Vtg The Boy Blue Oval Bubble Convex Glass? Miniature on Wood Painting by Thomas Gainsborough measures 4" x 5.5" x .75" oval tin topped decorative embossed raised frame. Original painted in 1770 tin is starting to raise on corners, it is in good condition for age. Per the handwriting on the back this was purchased at the Chicago World's Fair in 1933.