"The man" has to be able to prove when your mag was made. In the case of Ruger bx-25's that's easy because they have only been made a short time so there is no way there are any pre 1994 mags. Now AR-15 mini 14,mini 30, Beretta 92's, Glock, etc,etc, and aftermarket brand mags are a different story, how many millions were produced before 1994? Again unless it's a brand that wasn't manufacturing before the ban went into effect they have nothing to arrest you for. After the ban went into affect until it sunseted mags were marked "restricted for LE, military use or export only". When the ban sunseted some states kept the ban therefore any marked mags are a no-no in the "banned states", But when the warnings came off the mags unless they have a serial number or date of manufacture on them it cannot be proven when they are made therefore impossible to tell pre94 from post 2004. I Hope that helps.
NRA Life Member