This post is old but in order to know choke you also have to know bore size. Sticking one of those Galazan brass gages or any stepped gage in the end of the barrel is only telling you it has choke.
Prime example I had a 16 gauge that originally came with 26" barrels, now cut to 24 3/4". This gun originally had the .650 bore size to choke area which was changed in the mid 30's. The constriction in both barrels was .014. A Galazan gage stated full choke.
Taking a choke gage to a show or auction will again only show you that it does or does not have any constriction.