I’m doing some research and would like to know the exact date this “Games Expo” occurred, however, Googling “Games Expo 2007” reveals over 10 different results. I’m assuming it’s Origins, but I’m a bit confused because there’s a separate Origins-stamped Ditto:
Does anyone know which “Games Expo” this Squirtle-mimicking Ditto comes from?
“07 Games Expo Squirtle Ditto promo card. These cards were only given out to those that attended the 07 Games Expo in LV back in March. This was the first & last year the Games Expo will be held”
www.worthpoint.com/worthopedia/pokemon-ex-delta-species-ditto-games-137797491
Thank you, that’s awesome!
I found this article which says the exact dates of 18th-22nd March 2007: www.prweb.com/releases/2006/12/prweb491446.htm 
It could have been at others too but this is the only one I found that was specific.