I have been researching the legality of P99 hi-cap magazines. and here is what I have discovered.
A few years back, there was a "loophole" in the hi-capacity magazine ban, that was exploited to make 100% legal hi-cap magazines available, even for pistols made well after '94.
I will try and explain this "loophole", which was closed btw, so this is no longer legal.
The "loophole":
While the manufacture of new hi-capacity magazines is illegal, you can re-build existing magazines to like new condition. You can replace a worn out magazine body, followers, springs etc.. This is still legal, you can still buy "replacement" magazine tubes, springs, followers etc. (at the manufacturers discretion). But you must destroy the old magazine, and the re-built magazine must be for the same firearm. Here is the "loophole", the old law did not specify that the "re-built" magazine had to be for the same firearm. So people were buying up surplus AK-47 magazines at $10 apiece or so, destroying them, then "re-building" them into P99 magazines.
Hence you destroyed a cheap AK-47 magazine, and "re-built" it as a new AK-47 magazine, that just so happened to fit a P99.
Clear as mud?
So the legality of the unmarked magazine tubes is not-definate, and therefore un-prosecutable.
Even the magazines with the patent date showing post '94 production, are legal, if they were "re-built" AK-47 magazines.
So, the date of the magazine tube manufacture is irrelavent. If there is any question as to legality, it would rest with the person who legally (at the time) re-built the magazines.
And since there is no paper trail required by the law or the ATF for the re-built magazines, once again prosecution would be impossible.
This has been verified thru many different sources.
This is the reason for the ATF's "hands off" policy towards any unmarked hi-capacity magazine.
Anybody with more info, please add.
A few years back, there was a "loophole" in the hi-capacity magazine ban, that was exploited to make 100% legal hi-cap magazines available, even for pistols made well after '94.
I will try and explain this "loophole", which was closed btw, so this is no longer legal.
The "loophole":
While the manufacture of new hi-capacity magazines is illegal, you can re-build existing magazines to like new condition. You can replace a worn out magazine body, followers, springs etc.. This is still legal, you can still buy "replacement" magazine tubes, springs, followers etc. (at the manufacturers discretion). But you must destroy the old magazine, and the re-built magazine must be for the same firearm. Here is the "loophole", the old law did not specify that the "re-built" magazine had to be for the same firearm. So people were buying up surplus AK-47 magazines at $10 apiece or so, destroying them, then "re-building" them into P99 magazines.
Hence you destroyed a cheap AK-47 magazine, and "re-built" it as a new AK-47 magazine, that just so happened to fit a P99.

So the legality of the unmarked magazine tubes is not-definate, and therefore un-prosecutable.
Even the magazines with the patent date showing post '94 production, are legal, if they were "re-built" AK-47 magazines.
So, the date of the magazine tube manufacture is irrelavent. If there is any question as to legality, it would rest with the person who legally (at the time) re-built the magazines.
And since there is no paper trail required by the law or the ATF for the re-built magazines, once again prosecution would be impossible.
This has been verified thru many different sources.
This is the reason for the ATF's "hands off" policy towards any unmarked hi-capacity magazine.

Anybody with more info, please add.