The federal AWB was never as neat, complete, nor all-encompassing as either side depicted it.
The requirement to mark any new "forbidden fruit" was poorly followed at best, and impossible at worst.
How bad was it? Well, the government contractor for disintegrating MG belt links in both 7.62nato and cal..50 had to wait 9.5 years for ATFE to give them a "permission slip" to sell links to the government. (They were allowed to put a date & serial on the cardboard bulk box they were sold in, this despite the specific legislative language to the contrary.)
Now, the fact that no one in the legislative process realized that a belt link is a device "...which can readily be assembled...into an ammunition feeding device...able to hold more than ten rounds..." was typical of the pig-headed way all such legislation gets made.
That pig-headedness then became fodder for endless, and utterly irresolvable arguments over "glitch" versus "feature," which exist to the present day. And, in many extents, continues from the way too many State AWB just "xeroxed" the fed AWB language. Sadly, Occam's Razor cannot cleave "ignorance" from "malice" in such matters, so both "our side" and "their side" both persist in various forms of 'conspiracy theories' to this very day.
To OP's point, though, I've seen, at various gun shows, rather a lot of "pre ban" magazines offered for sale, almost always AR mags. I've not seen any at inflated prices of late, though. Despite the number touting "genuine Colt" provenance for the mags. Now, I note that all of the ones I have seen have had very used bodies, and good-as-new floor plates, and almost always, well-used green followers.
Which, then, makes me recall all the post-ban "follower color" fads. And where otherwise NIB mags would have the "old hotness" follower removed to substitute the "new hotness" color, and for, typically, a 50% markup. (There would be bag & boxes of the old color followers on the same tables--pay no attention to the man behind the curtain despite there not being a curtain).
It's all really rather inane, what with only the tiniest fraction of "feeding devices" were ever stamped for either date, or "restricted use" (or both), making pre-ban indistinguishable from "post ban." (Mirroring the time where various rifles were being offered, typically at inflated prices, as "pre ban" as if that had any significance where they were legally for sale.)