I got the Venetian NCV's at the hotel several years ago. As I recall, several 5's were your prize for sitting through a time-share presentation down the street (across from Polo Towers). There was a booth to sign up at the top of the Venetian escalator just as you enter the shopping area on the second floor.

The 25 and 100 were for casino invited guests; you picked them up at the cage after checking into the hotel. They were for two different promotions as I recall.