Physicist John F. Asmus, who pioneered laser-restoration techniques for Renaissance art, and who had previously examined the Mona Lisa in the Louvre for this purpose, published a computer image processing study in 1988 concluding that the brush strokes of the face in the painting were performed by the same artist responsible for the brush strokes of the face of the Mona Lisa in the Louvre,[19][9] and replicated that finding in a 2016 study.

[29] Physicist John F. Asmus, who had previously examined the Mona Lisa in the Louvre and investigated other works by Leonardo, published a computer image processing study in 1988 concluding that the brush strokes of the face in the painting were performed by the same artist responsible for the brush strokes of the face of the Mona Lisa in the Louvre.

[31] Asmus observed that "the Isleworth figure has a somewhat higher forehead, a slightly wider face, and less of a bulge in the veil over the proper left side of the head".

[30] John Eyre reported Adolfo Venturi, in his early 1920s examination, praised "the beauty of the eye drawing... is the principal portion done by Leonardo together with the line of the mouth".

[32] Italian curator Lorenzo Cecconi, who also examined the painting in the 1920s, said that "the fusion of the tints of the flesh, especially in the eyes; the line which designs the nose, the mouth, and the oval of the face" were remarkable, and indicated that "this may be a second work of the Great Leonardo".

[7] In the 1960s, the art dealer Henry F. Pulitzer claimed that "densitometric tests on the planes of face and hands show a gradual change of tone values from dark to light which only [Leonardo] da Vinci, with his amazing eyesight, was capable of".

[30] Other differences have been observed with respect to aspects of the face: The Louvre picture, whether from cleaning or some other cause, shows a bulge over the left eye which is anatomically impossible—a blemish which is absent in the newly discovered version, while the line of the jaw is not cut in so suddenly against the chin.

[35] Asmus specifically asserted that "portions of the hands in the Louvre painting have been criticized as being 'fat and ugly'", while "it is intriguing to note that the Isleworth thumb is more slender and closer to what would be expected from Leonardo".

[31] Cecconi observed that "the locks of hair falling on the right shoulder" did not correspond exactly to those in the Louvre's Mona Lisa, and that "the border around the neck differs in small details".

[7] Kemp considered certain elements of the clothing to be lacking, particularly in the rendering of the veil,[24] while professors Salvatore Lorusso and Andrea Natali of the University of Bologna, examining multiple portraits sharing the theme of the Mona Lisa, write of the Isleworth painting that "additional impressive features are found that can only be attributed to the hand of a great master", including "details in the rendering and design of the embroidery on the dress, which suggest a brilliant mind".

Pietro de Nuvolaria had written in a letter that "two of Leonardo's pupils were painting portraits which he occasionally worked upon himself", suggested as possibly referring to versions of the Mona Lisa.

[45] Proponents of the Isleworth point to the account of sixteenth-century biographer Giorgio Vasari, who wrote of the Mona Lisa that "after he had lingered over it four years, [he] left it unfinished".

[46] The record of an October 1517 visit by Luigi d'Aragon states that the Mona Lisa was executed for Giuliano de' Medici, Leonardo's patron at the Belvedere Palace between 1513 and 1516[47][48][a]—though this has been suspected an error.

[52][53][21][54] Experts universally agree that Raphael's pen-and-ink sketch, in which the columns flanking the subject are more apparent, is based on Leonardo's portrait.

[64] The hypothetical first portrait, displaying prominent columns, would have been commissioned by Giocondo circa 1503, and left unfinished in Leonardo's pupil and assistant Salaì's possession until his death in 1524.

[1] A record of holdings of the Avishays Estate in Chard, also mentioning Marwood, includes an 1858 entry for "[c]atalogues of plate and china, and of furniture etc.

[68] In 1913, English connoisseur and art collector Hugh Blaker spotted and acquired the painting from a nobleman's house in Somerset where it was said to have been hanging for over a century.

[72][29] Konody wrote that the reception of the painting had been marred by "some press agent who sent out the news broadcast, with wrong statements, misquotations, and other blunders galore", but nonetheless found that "though not altogether from the hand of Leonardo da Vinci himself, it emanates most certainly from his studio and was very largely worked up by the master himself".

[75] Kemp notes of Eyre that "His little book of fifty-one pages is full of careful scholarship, and makes about as good a case as can be made".

[76][77][78] Blaker's step-father, John Eyre, also believed in its attribution and claimed that the painting was an earlier version of Leonardo's Mona Lisa at the Louvre.

[33] According to journalist Dianne Hales, however the attributions based on connoisseurship evaluating sections of the painting such as face, hair, hands, and background failed to win a consensus as to authenticity at that time.

[33] Jean-Pierre Isbouts notes of Pulitzer that despite his success as a publisher he was "not a very talented author", concluding that "[h]is unfortunate 1966 book about the painting, filled with uppercase screeds... did far more harm than good, and ensured that no self-respecting art historian would go near the work".

[37] When Pulitzer died in 1979, his partner, Elizabeth Meyer, inherited the painting and after her death in 2008, the Isleworth Mona Lisa was sold to a group of Geneva-based investors.

[76] Konody, after his own examination of the painting, wrote in The New York Times that the discovery of the painting had been marred by attendant publicity, stating that "skepticism turns into hostile incredulity, if the discovery is injudiciously exploited by some press agent who sent out the news broadcast, with wrong statements, misquotations, and other blunders galore", but nonetheless finding that "though not altogether from the hand of Leonardo da Vinci himself, it emanates most certainly from his studio and was very largely worked up by the master himself".

[80] Art historian Martin Kemp notes that "His little book of fifty-one pages is full of careful scholarship, and makes about as good a case as can be made".

[82] When Henry Pulitzer purchased the painting in 1962, he immediately endorsed the attribution of Eyre, stating the Isleworth was the only Mona Lisa done by Leonardo.

Kemp wrote that at a 2012 conference, art historians and Leonardo experts Alessandro Vezzosi and Carlo Pedretti "made encouraging but noncommittal statements about the picture being of high quality and worthy of further research".

[95] In October 2013, Jean-Pierre Isbouts published his book The Mona Lisa Myth[96] examining the history and events behind the Louvre and Isleworth paintings and confirmed the latter's attribution to Leonardo.

[21] Isbouts states that testing of the canvas underlying the painting "revealed a detailed underdrawing with revisions", which he asserts are indicative of an original work rather than a copy.

[104] It has also been noted, however, that Leonardo visited Venice in 1500, at a time when oil painting on canvas was quickly coming into vogue there, "being lighter and more manageable.