Sotheby's will auction off Apple's first computer this month in New York. Though the clunky 1976 model may be sorely outdated, it has become an iconic piece of computer history.

The Apple I circuit boards, which were hand-built built by Apple co-founder Steve Wozniak, shipped without a monitor, keyboard, case or other features of a full computer kit; it was up to the user to assemble the rest. This forerunner to Apple's personal computing devices did not have the sleek design, power or functionality of, say, the MacBooks we know today.

The operational computer set up for auction includes an Apple-I circuit board, microprocessor, video terminal, keyboard interface, memory chips and cassette interface. Sotheby's expects the item, which also comes with the original manuals in fair condition, to fetch between $120,000 and $180,000.

When the model first debuted in 1976, simplicity was the name of the game. Apple I used fewer components than its competitors and stayed on the market until the next year, selling for $666.66. The next generation, called the Apple II, was ready-to-go right out of the box and remained the main source of revenue for the company for years, until Apple revealed the Apple III in 1980, the same year the business went public. Apple III was followed by Lisa, which pioneered tech terms like "mouse," "icon" and "desktop," which are now staples in our computer vocabulary.

According to the Sotheby's listing, about 50 Apple I computers remain in existence, but only six are known to be in working condition.

Mike Willegal, an engineer who has indexed 42 Apple-I computers, said that number of working computers is a pretty good estimate.

"If a unit hasn't been powered up in more than five or 10 years, it probably shouldn't be counted as currently working. These old computers tend to fail over time, even if they are just sitting on a shelf," Willegal told Computer World.

Christie's auction house sold an Apple I computer in 2010 for about $210,000. The model was expected to sell for as much as $242,000.

A private four-page memo written by Steve Jobs while he worked at Atari is also up for auction. The piece is expected to sell for $10,000 to $15,000.

Flip through the gallery below for our roundup of the 10 most iconic Apple products, Apple I included.

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  • 1. Apple I (1976)

    Apple's first product was a computer for hobbyists and engineers, made in small numbers. Steve Wozniak designed it, while Jobs orchestrated the funding and handled the marketing.

  • 2. Apple II (1977)

    One of the first successful personal computers, the Apple II was designed as a mass-market product rather than something for engineers or enthusiasts. It was still largely Wozniak's design. Several upgrades for the model followed, and the product line continued until 1993.

  • 3. Lisa (1983)

    Jobs' visit to Xerox Corp.'s research center in Palo Alto inspired him to start work on the first commercial computer with a graphical user interface, with icons, windows and a cursor controlled by a mouse. It was the foundation for today's computer interfaces, but the Lisa was too expensive to be a commercial success.

  • 4. Macintosh (1984)

    Like the Lisa, the Macintosh had a graphical user interface. It was also cheaper and faster and had the backing of a large advertising campaign behind it. People soon realized how useful the graphical interface was for design. That led "desktop publishing," accomplished with a Mac coupled to a laser printer, to soon become a sales driver.

  • 5. NeXT Computer (1989)

    After being forced out of Apple, Jobs started a company that built a powerful workstation computer. The company was never able to sell large numbers, but the computer was influential: The world's first Web browser was created on one. Its software also lives on as the basis for today's Macintosh and iPhone operating system.

  • 6. iMac (1998)

    When Jobs returned to Apple in 1996, the company was foundering, with an ever shrinking share of the PC market. The radical iMac was the first step in reversing the slide. It was strikingly designed as a bubble of blue plastic that enclosed both the monitor and the computer. Easy to set up, it captured the imagination just as people across the world were having their eyes opened to the benefits of the Internet and considering getting their first home computer.

  • 7. iPod (2001)

    It wasn't the first digital music player with a hard drive, but it was the first successful one. Apple's expansion into portable electronics has had vast ramifications. The iPod's success prepared the way for the iTunes music store and the iPhone.

  • 8. iTunes Store (2003)

    Before the iTunes store, buying digital music was a hassle, making piracy the more popular option. The store simplified the process and brought together tracks from all the major labels. The store became the largest music retailer in the U.S. in 2008.

  • 9. iPhone (2007)

    The iPhone did for the phone experience what the Macintosh did for personal computing - it made the power of a smartphone easy to harness. Apple is now the world's most profitable maker of phones, and the influence of the iPhone is evident in all smartphones.

  • 10. iPad (2010)

    Dozens of companies, including Apple, had created tablet computers before the iPad, but none caught on. The iPad finally cracked the code, creating a whole new category of computer practically by itself.