I had this info PM'ed to me on AR15.com
Law Enforcement Carbine. This specially designed law enforcement weapon system features many of the combat proven advantages of the military M4 carbine and is designed for tactical deployment and traditional patrol. It offers a semi-automatic only mode. The Law Enforcement Carbine rifle is also available with a step-cut barrel that allows it to accept a grenade launcher for nonlethal options. We sold approximately 4,100 units of the Law Enforcement Carbine in 2004.
It is from here:
There is a good bit of info there.
I think the rifles or rifle parts that are made in Canada have the Diemaco stamps on them. There have been a few on AR15.com that got Canadian Bolts or carriers in their rifles, and a few reported getting actual 6920's stamped made in canada.