Brown 2225B?

[rprosperi]

(06-26-2016 04:22 PM)Dave Frederickson Wrote:  I thought it might be a component of a larger system, like the HP 5890A Gas Chromatograph, which has HP-IL. The model numbers both end in "90A" which may not simply be a coincidence.

I believe this is exactly correct. In the 80's HP sold suites of products as a larger system (like the example GC system you mention) and often renumbered the 'standard' components to prevent folks from knowing they could replace components with easy to find off the shelf parts (in this case a 2225B), but there were also cases where these renumbered components had technical modifications tailored for the type of system they were used in.

As an example, this 'special' ThinkJet may have used a non-standard Character set, including special graphics characters used in the GC application, allowing them to build this special product out of nearly standard components