OK, I just went thru my stash of spare PCI cards. Of the 3 sound cards, 2 video cards, and 5 NICs, 7 of them have an extra slot cut in the card edge with the contacts, 3 of them only have 1 slot in the normal position.
All of these cards function perfectly, whether they have the extra slot or not.
Slinky, could you take a pic of the two cards next to each other so that we could compare the connectors? If you don't have a digital cam, a flatbed scanner takes pretty good pics of circuit boards