I never noticed this until I changed the spring. The magazine is stamped 9/94 and has follower #5. The others are follower #6. Interesting stuff.As far as the old "law enforcement only" mags, those haven't been made since at least 2004 and the majority are going to be older, possibly going back to 1994. Those magazines can't be updated past follower # 5; Glock redesigned the interior of the magazines, I forget exactly what they changed, but the redesign started with follower #6.