The machine - one of only a handful of fully-functioning models known to still be in existence - was designed by the Apple co-founder Steve Wozniak and went on sale in 1976 for $666.66.
In an email to the BBC this week, he said: "The Apple-I was ghastly underpowered compared to the Apple-II.
"But this Apple-I computer showed the world the formula for an affordable USEFUL computer."
It's thought that Wozniak and his business partner Steve Jobs sold around 200 of the computers in just under a year, helped by a deal with a local computing store based in Palo Alto, California.
According to an unofficial online registry - which is not affiliated with Apple - it's believed only 79 of the machines are still around today.
This model was sold at auction in Boston, Massachusetts on Tuesday (25.09.18), with an "anonymous businessman" placing his winning bid online.
RR Auctions' Bobby Livingston said: "It's a marvellous piece - and this one works! Our experts tell us that there might be 15 in the world that work properly. You can power this thing up and behave like it's 1976. It's pretty fantastic."