As in their numbers?
My method is to multiply their pokedex number by 10, and then +100 for each generation. (eg. Celebi is 251, so 2510, +200 for gen 2, = 2710)
Then check every odd number (every 8th file is a model, all models are odd numbers, so open 2711, 2713, 2715 and 2717 and one of them...