[drcy]

A lot of scientific technology and analysis has been invented and developed over time. 1958 was a long time ago in that respects.

Beyond stuff such as carbon dating and spectroscopy (atomic testing used to identify the chemicals in paintings), there are now artificial intelligence programs that analyse brush strokes and composition details to help identify the artist. As with autographs, artists have subtle minute and stylistic habits that even they are often not consciously aware of. They've done tests on the programs with known real and fake paintings, or paintings by two different painters, and the programs have been excellent (if not perfect) and separating the wheat from the chaff by examining minute details and patterns unnoticed by human eyes. They've been shown to even work with Jackson Pollack paintings.

In the 1930s, they would date a painting by rubbing alcohol in a spot of the oil painting and seeing if a needle would push through. As oil paint is very slow drying (we're talking decades to completely dry out) it's not an unworthy test (and could still be used today by the average antique store collector on that $200 painting), but it's primitive and one famous Pre-WWII forger beat the test by adding hard drying Bakelite plastic to his paint. Obviously, things have advanced since the needle test.

But I don't know the specifics about this particular painting and its history and the changing opinions. For $450 million, I would hope people were pretty sure.

Beyond determining the age, studying the style and brushstrokes to identify the actual artist has long been a thing. In Rembrandt's day, and with Rembrandt, the students of the master painter would copy the master's paintings under the master's watchful eye as their education. That's how they learned painting. As their payment to the teacher, they would give him their copies, the teacher would sign and sell them. So, for today's authenticator, there are fake Rembrandts that will scientifically date to the correct period and with authentic Rembrandt signatures on them. It takes stylistic analysis of the painting and brushstrokes to identify the real from the fake.