As stated by many... newspapers, photos, engraving... it can all be done post fact and not definitive "proof" of anything. You would be required to enter a sworn statement that they are accurate and authentic. That is the "proof" part as a sworn statement is a legal mechanism recognized by the courts as "evidence".
Remember when your word was your bond and not everyone was willing to impune their honor by providing false statements? The courts where founded on that and must still abide by it... unless proven false... for which you would face legal charges and penalty for making a false statement under oath.
By providing more info than is required it "can" open up more avenues for a prosecutor to prove your statement false or to at least cast doubt. Find one mag you forgot to engrave... the counts don't match exactly because you threw out a problem child, botched a mag mod, or gave some away... find just one hole in your provided "proof" and all the rest becomes suspect.
Why do it when all that is required is your swore statement, anyway. "I aquired every one of them pre ban". Your statement is "proof" accepted by the courts and it then falls to the prosecutor to prove your statment false with nothing physical to debate, cast doubt or unravel. IE., "the defendant is computer savy and altering metadata is well within his/her ability. He/she participated in a forum thread directly related to providing mag ownership proof where altering metadata was discussed."
See where that's going?
KISS
Don't sweat it. Don't provide anything more than is required by law that may potentially shoot yourself in the weewee.
Remember when your word was your bond and not everyone was willing to impune their honor by providing false statements? The courts where founded on that and must still abide by it... unless proven false... for which you would face legal charges and penalty for making a false statement under oath.
By providing more info than is required it "can" open up more avenues for a prosecutor to prove your statement false or to at least cast doubt. Find one mag you forgot to engrave... the counts don't match exactly because you threw out a problem child, botched a mag mod, or gave some away... find just one hole in your provided "proof" and all the rest becomes suspect.
Why do it when all that is required is your swore statement, anyway. "I aquired every one of them pre ban". Your statement is "proof" accepted by the courts and it then falls to the prosecutor to prove your statment false with nothing physical to debate, cast doubt or unravel. IE., "the defendant is computer savy and altering metadata is well within his/her ability. He/she participated in a forum thread directly related to providing mag ownership proof where altering metadata was discussed."
See where that's going?
KISS
Don't sweat it. Don't provide anything more than is required by law that may potentially shoot yourself in the weewee.