The hardware had been in the possession of Nine Tiles, a company responsible for the BASIC ROM in the ZX80 and ZX81 and called upon to provide the new BASIC for Sir Clive's new colour computer. Judging by labels on the ROM chips, the computer dates from around July 1981.
The Register had a chat with museum curator and CEO Jason Fitzpatrick, who told them the hardware had been fired up at some point in the past, and that the museum hoped to bring it back to life in the coming weeks, if the silicon cooperates.
And the value? In world where a working Apple 1 board can fetch $350,000, it's difficult to put a price on the one-off. Fitzpatrick remarked "It's in the eye of the beholder."
Yes I behold this computer with awe. The ZX81 (its predecessor) was the second computer I owned and where I really cut my teeth on programming in BASIC and hex. The ZX81's and ZX Spectrums launched many a successful computer career back then by sparking interesting in young minds.
See www.theregister.co.uk/2019/03/… and don't miss the video at the bottom of the article