As a matter of course, I've copied John's question (and the reply) re. droid factory from the Cantina.
Thingus:
What kind of droids are built on the production line, and do we see them entirely assembled? Also, do we know much about the paticulars of the construction line, like if the droids are checked for correctness before they leave our site?
GM:
All that a prisoner could discern for themselves is the assembly of the parts they work on. However, it's no secret among the prisoners that the facility builds construction droids. After a day's work, you leave your station with completed parts still there - they're removed by members of staff after you've left, and no quality checks are done in the time between completing a part and you leaving your station - any correctness checks that may be done, you've never witnessed. if there are any, they're done elsewhere.