Homebrew Z80

[Brad H]

Hey guys.. I bought this Homebrew Z80 machine from what I assume is the
early 80s (going by the chips).  Pretty sure it's a Netronics keyboard but
wondering if any of you have seen a design like this one.  I'm just curious
if it came from a magazine article or something as it goes beyond the
typical basic homebrew and even appears to have some ROMs.  I'm not sure
what the TOS ROM is though.

 

I've put some pics of it here:
https://drive.google.com/drive/folders/0B4pq0-BHd2x6bjY3MTRZbGRCQmM?usp=shar
ing

 

Thoughts/opinions welcome.