It looks like they optimized this thing for low cost (thus the lack of silkscreen; words burned into copper), but at a low production run as well (thus the EPROM). Dang, if only startups thought like that these days
Ugh, I'm so utterly fascinated by this thing! OK, so I dug a bit (er, a lot) with Google-Fu. Since much of the world revolved around magazines at the time (great places for a glimpse into the past!), I started with a search on Google Books, centered between 1/1/1981 and 1/1/1990. I ended up with not much... in fact, not a single mention of "Computek" in all of PC Magazine. So, they weren't much a consumer-facing device, that rules out a consumer device...
I found a reference to a Computek in a number of places - one referenced to a factory in Canada and being a case study in manufacturing (interesting...?), but book snippets were cut too short to make out many details. Another reference was to a Computek in Burlington, MA in the 1981 time period. Interesting... and that led me to a patent from Computek, maybe related, but maybe just a loose end:
http://www.freepatentsonline.com/4281393.pdf
Still digging on more Computek info - knowing what they made will definitely lead to knowing what this thing is for
edit: okay, Computek in MA
dates back to 1977, before the IBM PC was even created that led to the ISA connector this thing uses. Not sure if I'm onto something...
edit:
Computek was around 'til 1990. Definitely the right one.
edit edit: my search seems to end at a reference to a "Computek Publisher Four" computer system in 1984, referenced in a fantastically specific way in
Microcomputer Market Place only in my Google results snippet as "Product Name: Computek Publisher Four RAM: 96-256k bytes ROM: 16k bytes Operating System(s): CP-M $6500.00". I might just go to the Palo Alto library just to browse and find this reference on paper, haha...
edit^3: Okay, now digging into the board layout itself. I arranged the two photos side-by-side and mirrored the back side so it overlaps the component positions on the front side (easier to flip back and forth to analyze).
That EPROM layout is very strange to me (why would it need a 74 logic chip in such a simple design?). I'm about 100% certain the earlier-linked
datasheet is correct. It references this specific chip, and in doing so, it says that the 8039 is used only with external program memory - OK, cool, that's what we've got. But what I don't understand is the odd layout... datasheet says that DB0...DB7 and P20...P23 are used as address inputs to the external memory during a fetch, then (implicit) the DB0...DB7 pins are used as inputs for the resulting data. Strange to use the same pins as both address output and data input... but I don't see any of that happening on the board here. I can't see where the traces go under the MCU, though... maybe they're routed under it, to the extreme left and between the pins there? (they seem to route P10...P17 on the back side)