This early issue 2 Spectrum has some modifications to the system board (pictured). Serial number 001-019020. Kindly donated by Ruth Bramley.
The modification is known as the cockroach mod, it fixed some bugs in the ULA, only issue 1 and early issue 2 machines have this ULA.
Early issue 2 boards such as this, that use parts left over from issue 1 production are dubbed issue 1.5 by the Spectrum community to distinguish them from the later issue 2 board.
ZX Spectrum Issue 2 With ULA Modification Manuals:
ZX Spectrum Issue 2 With ULA Modification Articles:
Magazines RELATED to ZX Spectrum Issue 2 With ULA Modification in our Library
Other Systems Related To ZX Spectrum Issue 2 With ULA Modification:
This exhibit has a reference ID of CH32957. Please quote this reference ID in any communication with the Centre for Computing History.