So i sat here this morning with a bag of 50 crystals playing a game of what is the resonant frequency. Thoroughly boring I can assure you and I am not sure how the ladies at uBitx Labs in India can sort through thousands to get sets of 8. But alas I have done enough for now to get 2 sets that are matched at a guess to within 50hz, being that my frequency counter is only good to 100hz.
One thing that I would not have predicted is the distribution in the resonant frequencies. Its like buck shot, all over the place and the other thing I would not have predicted is the number of dead crystals or ones with so low Q they might as well be dead being 8, that seems like a very high death rate to me. I still have 2 more bags to sort, but thats not happening today, i have 16 matched crystals I need for 2 filters and am moving on to the next thing.