Today, Steve Jobs is regarded as the brilliant mind behind Apple, the most valuable company in the world.

But in 1976, when Jobs was in his early 20s, he made a much different impression: He seemed to be "flaky," and a "joker."

That's according to letters written by Mike Rose, a Silicon Valley advertising executive whom Jobs contacted to print the operating manual for Apple's first personal computer, the Apple 1.

Rose was suspicious of Jobs, who was unknown at the time, and he took notes on the conversation. He then passed them along to his business partner, "Bob" in a letter dated June 23, 1976.

"[Rose] writes about how there are two young guys in a garage," Leslie Berlin, the historian for the Stanford University Silicon Valley Archives says on an episode of "Recode Decode," adding that Rose said "sounds fishy. Watch out."