I can only find die cracks for the Denver mints,, for the other mints you have to go through all the listings and the SCRIBBLES listings....its very intense.....However SuperDave is very good with the 1921 series and he can give you some pointers.
Cracks are not enough to go by (for most of us that is!)

write a list of all doubling and such that you find, so people can help you search and figure it out...

.Good luck.......