A rare Apple 1 is up for auction. Bids are already over $270,000 with nearly a week to go.

A rare Apple 1 computer, possibly even a prototype, is up for auction on Charitybuzz; bids have already topped $270,000 with six days remaining.

The computer differs from many of the production units in ways experts say make it likely the unit is one of the earliest of the Apple machines.

“It’s the rookie card, for lack of a better word,” Apple expert Corey Cohen told Recode. The Apple 1 up for auction contains original manuals, a cassette tape with BASIC programming language and other accessories and documentation.

Cohen said most of the early machines were hand finished by either Dan Kottke or Steve Jobs, and there’s a good chance this one was put together by Jobs.

“Dan doesn’t remember assembling this one,” Cohen said, saying he talked to the early Apple employee about the machine up for auction. The BASIC cassette, which Kottke did create, contains the words “Good Luck” written in his handwriting.

Cohen said the original owner of the unit is not known. The present owner bought it back in 2000 for $18,000, then the going rate for such machines.

While it’s hard to say how much the machine will fetch now, other Apple 1s have garnered as much as $900,000. A portion of the proceeds from this auction are set to benefit the Leukemia & Lymphoma Society of Arizona.

This article originally appeared on Recode.net.