I thnk that you've got a self licking lollipop....a problem that'll solve its' self.
STI mags will have a "dull" almost sintered finnish.
SVI mags will have a "bright" almost chrome finnish.
As for which vintage is for what.....just figure which mags work for you and which can be adjusted to run or kept as spare.
If you're going to be in limited ( 10 rds)...that solves that issue.
If you're in Interational ( IPSC) competition...then the "box rule" applies accordingly.
If your in a place that has unlimited capacity ( 3 Gun or USPSA)...again go accordingly.
Hey, its hard enought to get these suckers to work 100%, so find the ones that will work for the games you wish to play.
Have a great winter season :devil: