In my company, we distinguish prototype from production prints by numbered vs. lettered revisions in the title block, and numbered revisions don't require an ECN in the title block. This allows us to efficiently track prototype revisions during the engineering phase and then maintain tight control on revisions during production. I think this is a very common practice.
However, when moving from one lettered Rev to the next, there must be a way to test out the new rev before finally releasing it. If I produce a part (say, circuit boards), I have to release a print to my circuit board vendor. The part is already at Rev A, so I can't do a numbered release. So now I have to release at Rev B - but now production sees a Rev B print in the system. I would rather production continues to see only Rev A until engineering is done testing Rev B.
Additionally, it is standard practice for us to print the part number and rev on circuit boards. So if the board says "Part Number-Rev B", production knows that lettered revs are good to use in their assemblies. So now a danger exists that if any of these parts make into a production bin, before testing is complete (or if the parts turn out to not work properly) there is no control to stop production from using them. If, on the other hand, they have a numbered rev, production knows not to use them except for engineering specified builds.
What is a recommended best practice for identifying prototype parts that are post-production release?
Note: Our assemblies are small, so we don't have room for a bunch of red tags, printed notes, emblems, or other things like that.
I can't find appropriate tags for this post - am I posting in the wrong community?