It's the kind of electronic junk that piles up in basements and garages - an old computer motherboard with wires sticking out.

But because it was designed and sold by two college dropouts named Steve Jobs and Steve Wozniak, it could be worth more than half a million dollars.

An Apple 1 from 1976, one of the first Apple computers ever built and forerunner of today's MacBooks, IPads and IPhones, goes on the auction block at Christie's next week. The bidding starts at $300,000, with a pre-sale estimated value of up to $500,000.

"This is a piece of history that made a difference in the world, it's where the computer revolution started," said Ted Perry, a retired school psychologist who owns the old Apple and has kept it stashed away in a cardboard box at his home outside Sacramento, Calif.

The 11-by-14 green piece of plastic covered with a grid of memory chips above a labyrinth of wires was one of the first 25 such computer elements, and sold for $666.66. About 200 were made but most have disappeared. Various estimates put the number known to still exist from about 30 to 50. They came with eight kilobytes of memory - a million times less than the average computer today.

- Associated Press