Lloyd Blankfein tweets photographic proof that he once had hair

• Goldman Sachs CEO Lloyd Blankfein tweeted his Harvard student ID.
• "#TBT Summer's over; back to school!" he tweeted.

Before he was the head of one of the world's largest investment banks, Goldman Sachs CEO Lloyd Blankfein was a mop-topped undergraduate at Harvard University with a concentration in social studies.

On Thursday, Blankfein shared a memento from his college days — his own Harvard student ID card — with his more than 50,000 Twitter followers.

Blankfein tweet

The card appears to be dated June 1975, which would make the young Blankfein in the photo 20 years old and a college senior, according to his Harvard alumnus page.

Above Blankfein's embossed name is his signature, which appears to have changed significantly in the 42 years since the card was made.

But the most discussed detail of the tweet, perhaps unsurprisingly, was Blankfein's long-departed hair:

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