Well, again, the Federal AWB ran from 1994 to 2004. The Model 6900-series guns were all discontinued during the ban. 12-round magazines made after 1994 and up until 2004 had to have the LEO/Export restriction on them. They are all "post-ban" magazines, by definition. For us common peon folks, we were only able to get 10-round magazines.... obviously without the LEO/Export markings.

2nd and 3rd Gen 69/6900-series 12-round magazines made before 1994 are the "pre-bans" and that is what you've got other than the LEO/Export marked 6, 7 & 8.

To the best of anybody's knowledge, S&W did not manufacture any brand new 6900-series 12-round magazines after the ban ended although there is speculation in some quarters that maybe they did because some would occasionally pop up for sale here and there. But even if they did, there is no known way to date them or to tell them apart from known pre-bans (as there is for other S&W pre-ban vs. post-ban magazines)... so it becomes kind of a moot point in a legal sense.

As for your .356TSW magazine, if it is not LEO/Export marked, it was very likely made in 1993... just before the ban.