The Apple-1 sported a circuit board hand-built by Apple co-founder Steve Wozniak, and first went on sale in July 1976 for $666.66. Roughly 200 units were produced, and according to Sotheby's catalog listing, there are roughly 50 surviving Apple-1 computers, with six of them known to be in working condition.

This means it's a great time to throw one of those six working Apple-1 PCs on sale, right? Well, the auction house is estimating the motherboard will sell for between $120,000 and $180,000. Crazy!

Mike Willegal, an engineer with a major technology company who has identified and indexed 41 Apple-1 computers says:

That's probably a pretty good estimate of original Apple-1s that have been operated in the last four or five years. 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.

The Apple-1 was sold as a fully-assembled circuit board, minus a case, power supply, keyboard or monitor. Unlike later Apple-based systems like the Apple II from 1977.