I am a Federal Inspector for NASA and the Department of Defense. My certifications are in Electronics, NASA Processing SMT, Polymeric Coatings, Soldering, etc... also Electrical, Mechanical, Ammunitions, Clothing and Textiles, Petrolium Products, Chemicals, Aircraft, Aerospace and Weapons Grade Software...whew...
We are the guys in the field that inspect any and all hardware purchased by the government, usually for DoD, if we see that the hardware is good, then we authorize payment to the contractor. I authorized 20 million or so last week, which is about average. Here is my agency
http://www.dcma.mil/
One cert I do not have is Nuclear, which requires you to be in the subject field day in and day out.
If some of you older guys remember the Apollo Program, DCMA QAR's were the guys in the white suits that were buckeling the Astronauts into their capsule, and closing it up...