From the very moment Picasso’s massive sculpture for Daley Plaza was dedicated on Aug. 15, 1967, interpretations have run the gamut.

But this week, as the city begins to celebrate the sculpture’s 50th anniversary, artist Herbert Migdoll, the veteran photographer of Chicago’s Joffrey Ballet, has suggested one of the most convincing explanations of the imagery behind Picasso’s work.

“Look at that horse head mask, and then look at the sculpture, and you see all the same basic forms,” said Migdoll. “I think that 50 years after he created the ballet designs, Picasso borrowed from himself.”

In 1917, an innovative ballet titled “Parade” was created for Sergei Diaghilev’s Ballets Russes, with music by Erik Satie, a scenario by Jean Cocteau, choreography by Leonide Massine, and sets and costumes by Picasso that made cubism part of the theatrical design vocabulary for the first time.

The work, which debuted at Paris’ Theatre Chatelet, didn’t receive its U.S. premiere until 1973, when the Joffrey Ballet reconstructed it with all the original Picasso designs.

Among the many figures in the ballet, which conjured a surreal performance by street performers, was a horse with a cubist, mask-like head. Migdoll’s photographs of that Joffrey production suggest that the mask is a very close relative of the enormous face Picasso would create for Chicago a half-century later. The artist essentially worked a giant variation on an image in his own vast archive.