AC Artshow Staff do it the same way, cards with numbers.
They using shelfs to store the goods.
Number ranges are related to ranges at the shelfs to lower search time.
I had heard that we were similar to AC in that regard, though the similarity was accidental. We brought it in, in the end, because of the sheer number of people we had coming in with cameras back in 2009. We just happened to have some raffle tickets lying around for some reason (I don't remember the con ever holding a raffle) and it made sense to use them at the time.
