ok, to start, i am one of the CHP gunsmiths.im not on this site a lot, but will try to answer some of your questions.
1. we had to start with ser.# chp1018 because the first 1000 serial #s had already been use and ended at chp 908a
2.the marks on the barrel crown are machining marks made at factory during the CNC process( worn bit, metal flakes during cutting.)
3.some mag.s are new as we will not be needing them
4.the first 4006 had a safety, the TSW is a spring loaded decocker. the spring and detent that's under the rear sight is a safetyincase the coil spring breaks.
5.we replaced the old 4006 because we were running out to issue cadets. waited to long to do a test.
hope this helps ;-)