My guess is that it came from a terminal + printer DECwriter; and that someone wanted to re-use the board with a CRT based terminal instead of the printer. Hence the new case, that the CRT could be placed on top of.
rootwyrm would probably like to see this.
Little late to the party but indeed, me likey.
Also, you are correct - that's a DECwriter board in a housing to rest a CRT on top of. Note the wiring inside - that's power and a DB25 direct to the board. No room for any other PCBs. And you see that sub-controller? I'm betting that's a code translator board, because this thing appears to be wired for a VT100-series (first models without an integrated keyboard.) My guess is somebody liked the DECwriter feel enough to do this.
The white and gold part there in the center is what makes it rare and unique - that's likely a Zilog Z80 or Intel 8080 doing duty as the code translating processor. So yeah, custom keyboard controller in a custom housing back around I'd say mid 80's possibly. (I don't see a UVEEPROM tho, so not sure how they're doing code storage.)
