1453 is my choice, when the second capital, Constantinople fell and that was the end of the Roman Empire. The art changes by the end, the concept of spiritualism came to the art of coins, the figures are made crudely because all true beauty lies within.
I have the guy who ended the Empire in 1453 CE... Ottoman Turks Sultan Mahmed II 1451-1481 took Constantinople in 1453 Serez mint AR 1.2g
And here's that conqueror, Mehmet II's portrait on a Renaissance medal (about 1490 according to the description), that was made after Gentile Bellini's marvelous life portrait, painted in Istanbul 1480. I photographed it in the Museo Correr, Venice, last Monday (with my Iphone resting on the glass case).