Not trying to be difficult, but I looked at your ad and was confused, based on my understanding of GLOCK magazine generations.
I have generally used the following guidelines:
It is generally accepted that there are 4 generations of GLOCK magazines:
Generation 1 -- Not fully metal lined (NFML) -- Designed that way to allow partially the magazines to "swell" slightly when loaded to prevent accidental dropping of the mag from the pistol if the mag release is inadvertantly depressed. Also known as Non-Drop Free mags, but this is a misnomer, as many NFML mags will Drop Freely from the pistol when approximately 1/2 the capacity of rounds or fewer remain in the mag and the mag release is depressed. These are particularly identified by the " U " notch at the top of the magazine spine. NFML mags were made prior to the 1994 Clinton AWB.
Generation 2 -- Fully metal lined (FML) -- Designed to maintain shape without swelling when fully loaded in order to "Drop free" when the mag release button is depressed, no matter how many rounds remain in the mag. Thus these are AKA "Drop-Free" mags, but this is also a misnomer, as some FML mags still do not drop freely from the pistol due to tolerances, temperatures, etc. This generation is distinguished by the " l__l " notch at the top of the magazine spine. These are also preban.
Generation 3 -- FML -- Generally the same as Gen 2, but these are identified by the " \__/ " notch at the top of the mag spine. Now, this is the generation which causes the most confusion as to pre-ban/post-ban. Preban versions of this generation have the caliber designation marked approximately 1/2 the distance between the topmost witness holes and the notch at the top of the mag spine.
The next variant in this generation is marked "Resricted LE/Govt Only" and the caliber designation was moved up near the notch to make room for the restriction notice. This variant is restricted, thus post-ban.
The third variant in the 3rd Gen, looks like the other two, with the " \__/ " notch at the top and looks like the second variant with the caliber designation up near the notch. This magazine has no restriction markings, but there is room where such markings had previously been added. When the need for markings was removed with the sunset of the AWB in 2004, GLOCK left the caliber designation up near the top of the magazine spine, rather than re-tool to change the location of this marking. This variant is post-ban.
Generation 4 -- FML -- practically like generation 3, but the sides of the magazines have been contoured to make mag insertion easier. Also post-ban.