Isleworth Mona Lisa
According to Leonardo's early biographer Giorgio Vasari, Leonardo had started to paint "Mona Lisa" in 1503, but "left it unfinished". However, a fully finished painting of a "certain Florentine lady" surfaced again in 1517, shortly before Leonardo's death and in his private possession. The latter painting almost certainly is the one that now hangs in the Louvre. Based on this contradiction, supporters of the authenticity of the "Isleworth Mona Lisa" claim it is the unfinished "Mona Lisa", made at least partially by Leonardo, and the Louvre "Mona Lisa" a later version of it, made by Leonardo for his own use.
Portrait of Dorothea Berck
Portrait of Dorothea Berck is a 1644 painting by Frans Hals that is in the collection of the Baltimore Museum of Art. It depicts Dorothea Berck at age 51, the wife of the prosperous Haarlem merchant Joseph Coymans, whose portrait Hals also painted. Both paintings were executed on the occasion of their daughter Isabella's wedding, whose marriage pendants Hals also painted.
The painting, like many of Hals's portraits, is inscribed and signed, but there is no mention of the identity of the sitter, and it was only identified as Berck in 1908. 
The portrait is noted for its classical similarity to the Mona Lisa. Like the Mona Lisa, she sits upright in a dark chair and rests her hands on either a dark desk or perhaps a large dress that surrounds her. Her ungloved hand may be clasping a book or part of her sleeve. The loose brushwork is typical of Hals and shows a fleeting gesture with the casual way her finger is hooked over her wrist. Portraits of subjects with one glove on and one glove off are common in Dutch 17th-century marriage pendant portraits. Gloves symbolize the wedding vows where the husband and wife each hold one of a pair of gloves. In this case, her husband Joseph Coymans is wearing the "other glove" in his pendant portrait. In Hals' marriage pendant portraits, the husband is always situated on the left and the woman on the right, and the light always comes from the left, shining fully on the woman.