I found it again last week. It's a 1994 Toshiba T2100/260 - 486 with 4MB on-board ram, 262MB hard drive, 10" monochrome screen. No USB, No Ethernet. It has a couple of old serial/parallel ports and a PS2 port and not much else.
It turns on and sometimes shows a picture on the screen. I can't get into the bios with any combination of Esc, Del, Esc+F1 etc. If I leave the hard drive in, it never shows anything on the screen and the hard drive is very noisy. I think it could be failed RAM but it's integrated into the motherboard and the expansion slot is an old ram type I don't know about. The keyboard works because capslock lights up and it eventually beeps if I press too many keys.
It has two extra batteries in it, aside from the main power battery. One is a coin battery bigger than a CR2032 and the other is a nicad pack.
Having looked at the case, I think I would rather just keep a netbook in its original case.