A hoary old Apple I computer signed by Steve Wozniak is set to fetch at least $260,000 at auction.

The computer comes from the stone age of computing and dates back to 1976, when Steve Jobs had just gotten over his first few acid trips and was beginning to flog computers from his parents' garage.

The Apple godhead sold his beloved VW camper van to fund the first computers, while collaborator Steve Wozniak pawned his HP-65 calculator for $500 – worth over £1,800 in 2013 terms.

This particular Apple I comes with a letter signed by Jobs and the internal circuitry bears a scrawl by Wozniak which imaginatively reads: "Woz".

According to the auctioneers Breker, only six of the vintage computers are in working condition today, and this one is expected to net roughly €200,000 or $260,000. According to an earlier estimate from auction house Sotheby's, fewer than 50 of the original batch of about 200 Apple I units even exist, let alone work.

The advertisement for the auction says: "Original Apple I Computer from 1976. This is the sensational first product of today's highest-valued company ever. This Apple I set on offer here is 100 percent authentic and in full working condition.

"Already a legendary milestone from the dynamic dawn of the personal computer age."

Mike Willegal, an engineer who has verified and tagged 41 Apple I computers, gave the machine the index number 37.

"It's been cleaned up and brought into operating condition. I have no clue about what will win it, but it seems like the European auctions seem to be gathering the highest bids, so it may well reach its estimated value."

Breker sold an Apple I for $640,000 (£410,000) in December last year.

The auction house has put together a video of the Apple I booting up and then loading an eerie, blocky 8-bit image of Steve Jobs, followed by the Apple logo.

It also released images of the original manuals which come with the Jobs-signed letter, in which he offers to swap the motherboard of the Apple I for the latest Apple II version if the owner hands over £400.

The exact specs of this particular machine are unknown, but it will have been equipped with the 8-bit MOS Technology 6502 chip, running at 1MHz, and at least 4k of memory – just enough to save a copy of the Apple logo.

It originally went on sale for the creepy-sounding price of $666.66 - allegedly because Woz was fond of repeating numbers, not because he was a devil worshipper.

Jobs had clearly not yet developed his legendary flair for design when this computer was produced, as the Apple I came as a bare circuit board which could be plugged into an ordinary television. ®