An Apple I that is expected to fetch half a million dollars is currently on sale by Christies in an online-only auction. Some interesting Mac prototypes are also included in the auction, which ends on 9th July.

Apple 1s have been selling for high prices over the past few years. The record is currently held by the German auction house Breker which sold for almost $700,000 in May 2013, which beat its previous top price of around $630,000 achieved in November 2012. Prior to that an Apple 1 sold at Sotherby's in New York fetched $374,500 in June 2012 and Christies in London had sold one for over $212,000 in November 2010.

The Apple 1 that is part of the current online-only auction has an estimate of $300,000 - $500,000. It's motherboard is numbered 01-0025 on the reverse in black ink. This notation is  believed to have been written by the original retailer, the Byte Shop. However the fact that it does not have the diamond NTI logo of the PCB manufacturer tends to confirm it is indeed among the first 25 to be produced.

Its current owner Ted Perry, a retired school psychologist from Sacramento, California acquired the computer for nothing in a swap over 30 years ago. He believes it to be in working order.

The sale, FIRST BYTES: ICONIC TECHNOLOGY FROM THE TWENTIETH CENTURY, is taking place online. It opened on June 24th and different lots close at different time on 9th July. There are ten lots in total and all but two are Apple computers - the exceptions being a set of Early Apple II Software comprising EasyWriter and VisiCalc with an estimate of over $250; and a prototype learning computer from Tiger Electronics with an estimate of over $3,000.

Prototypes seem to be more valuable that production models with a 1984 prototype Apple IIc, a more portable version of the Apple IIe, having an reserve (opening bid) of $5,000; and a prototype   Apple IIGS, a more powerful successor from 1986, having an opening bid of $10,000. There is an Apple IIe in the sale, a  'revision B' version manufactured in 1983 or 1984 and its opening bid is only $300.

The Apple Lisa included in the line up has an opening bid of $20,000. It has the early idiosyncratic 'Twiggy' floppy drives that could store over 800 KB but required special diskettes which suggests it is a 1983 model.

There are three unusual Macs in the sale. One is a twentieth anniversary Macintosh one of a limited edition of 12,000 units introduced at the January 1997 MacWorld Expo in celebration of Apple's twentieth year as a company. Its current bid is $2,000 and the same amount applies to a pre-production prototype Macintosh Portable Computer. Finally there's a Translucent Macintosh SE Case which has a current bid of $5,000. Its notes state:

This highly unusual case is believed to have been custom manufactured by Apple Computer, Inc. as part of the development of the Macintosh® SE c. 1987, perhaps for checking airflow inside the SE, the first Macintosh with a fan.

If you are tempted by any of these historic items you need to create an account on the Christie's site and you can then view and bid for items - and see the results of the sale once it concludes.