Sinclair ZX80 questions

I've got a ZX80 here (issue 2A) which has a keyboard overlay attached that looks very like that of a Sinclair ZX81. The ROM in the machine is dated week 16 of 1981, and carries the marking C77018, and a 1981 copyright. Is this a machine that's been subjected to a ZX81 upgrade kit or something? I wasn't aware that such a thing existed. Now, the keyboard overlay's actually removable, revealing a pristine original ZX80 legend underneath. However, two black press-fittings attach it to the PCB at the corners of the front edge - are these press fittings there on all ZX80s, or have these been added in order to secure the overlay in place? The machine came with a "ZX 16K RAM" module (red lettering) which I assume is later and more in keeping with a ZX81? Separately though I do have a module marked as "ZX80 16K Byte RAM Pack" (white lettering). Question is, are they interchangeable and the lettering was altered - or does the ZX80 variant map memory to a different location than the later red-lettered type? (I'm assuming that the expansion bus pinouts didn't change between ZX80 and the later machines!) I've also got a ROM marked as: "ROM contents copyright 1980 Sinclair Research Ltd" - is this the original ZX80 ROM (and the ROM in the machine is an upgrade), or is this likely something else entirely? Curiously there are a few stray fibres glued to the underside of the PCB - presumably these are a left-over of cheap PCB manufacture and Sinclair's horrible quality control! :-) cheers Jules -- A. Because it destroys the natural flow of conversation. Q. What's wrong with top posting ?