So, with reading the above comments, here's my thoughts that no one asked for.
Lets be honest with ourselves. Your T206 Piedmont Cobbs, 34 Gehrigs, 33 Ruths, any year Mantle, Mays, Aaron, Robinson, etc.; these cards are simply not rare. Beautiful, wildly popular, expensive in some cases...absolutely; but not rare.
So if there are say 400 people across the US in any given year who want to auction their red piedmont Cobb, or 1,000 people who want to auction their Mantle, and only say 100 major auctions, what are said consignors supposed to do with these cards if the AH's will only ever accept one copy of each per auction? Should the sellers hold their card hoping sometime in the next five years that an AH will accept their 54 Robinson as the sole example in their auction? Or should they just try to sell the card themselves, which they clearly didn't want to do to begin with, because they can never get it accepted by an AH due to the flood of material on the market.
I can definitely see where it would be frustrating to consign your card to an auction, only to see six other examples in the same auction, but what are the
realistic alternatives? Like I tell my teams at work; don't bring complaints to the table if your not also going to bring ideas for a solution.
Not trying to stir the pot here, just posting a different point of view.