If you have pictures, I could tell for sure. The newer decks seem to be brighter somehow. I'm not 100% sure, but it looks like the older ones are CFL backlit and the new ones are LED, but I couldn't tell you that 100% for sure, just going by the color temperature of the backlight.
Just to get your terminology correct, there is no such thing as an alpha 1 iDeck. They are all Alpha 2. Bally made some iDecks that would fit on an alpha 1 cabinet, but unless you had the alpha 2 mpu and backplane, you would not have been able to use it, so they are in essence alpha 2 only. It was just manufactured to fit on the older V32 cabinets before the alpha 2 pro v32 cabinets were released. In fact you still see a LOT of alpha 1 V32 cabinets on casino floors today, they have had a long life and is a player favorite, and that's why the V32's are relatively expensive for the outdated alpha 1 platform.