John: Just some back ground information. In the last 4-5 years, the US had been purchasing many M14 items, in very small quantities. It is not like the 1960's when you would see a contract for 65,000 or 90,000. The recent contracts are usually a few hundred, or maybe a couple of thousand.
DPMS became a government contractor in 1985, so my guess is if the company produced the trigger housing, it was in the last 2-3 years. As I have not much interest in current procurement, maybe Different can zero in on when they were made (if that is an issue).
Have fun.