[CJefferson]

They could have typoed '664', which was the 464 with a floppy disk drive. However there basic was still in the ROM.

[ghusbands]

It was a typo for 464 - you can tell by the video it links to.

[Doctor_Fegg]

Indeed. I still have my 664 in the loft somewhere!

[UncleSlacky]

They're worth quite a bit these days as they were rapidly replaced on the market by the 6128 (which is in my loft).

[CJefferson]

Wow, I had no idea! There might be a 664 in box in my parent's house somewhere -- although it also might have been discarded some time in the last 20 years (as I imagine happened to many of them).